Finding the right QRP radio

So many radios... so little time

YouKits QRP rebranded as TenTec

When I was learning CW I had borrowed a friend's inexpensive Ten-Tec QRP radio.  I'm glad I had the opportunity to borrow it while I was trying to decide what type of radio to purchase. There are many, many options for QRP radios.  

I began by looking at the very inexpensive, simple radios kits like the Rockmite and TunaCans but decided my acumen with a soldering iron was likely insufficient for even something as simple as those kits.  I will probably look into building one of those eventually for fun.  Then I started looking at the more expensive pre-built QRP radios like the Ten-Tec 4030/4020 and Patriot but the more I listened the the little Ten-Tec the more I realized the limitations of these lower priced radios.  Just a couple of items to mention... the AGC (automatic gain control) was harsh.  Strong stations would pop into your ear like a needle before the AGC brought them under control.  If you turned on the attenuator that led to the problem of there being no independent adjustment for the sidetone.  So if you had to turn up the volume to copy a quiet station (with the attenuator on) the sidetone would then blister your ears.  It would do the job but it wasn't pleasant.

Some kits are more capable than others.  This Elecraft KX1 is a very capable radio built from a kit

Ten-Tec Patriot

I think it could be fun to use these inexpensive QRP radios as an added challenge but I didn't want an impediment to my entry to QRP and CW so I decided to spend more money and go with a better quality radio.  

Ten-Tec Argonaut V

Elecraft K1

Show me the Good Stuff

I kept seeing a couple of recurring themes in radio reviews to look for in a radio that is to be used primarily for CW: a smooth QSK and a quiet receiver.  In the past when I had my Yaesu and ICOM radios they used a mechanical relay to switch to transmit.  So when I would send CW the relay would audibly snap shut and when I'd pause it would snap open.  When you're sending CW it's polite to be listening between your words to see if a station wants to break in or answer.  This clatter of the relay in the radio during QSK becomes annoying (to me anyway) such that I ended up setting the delay longer and longer so that it didn't trigger.  At that point I was basically key-down until I finished transmitting which isn't terribly friendly in CW land.  So I wanted a radio capable of full-break-in QSK without relays.  That type of QSK seems to be standard on TenTec and Elecraft radios but isn't offered on "big brand" radios until you've worked into the very expensive models.

Another other aspect of a good radio for CW is a quiet receiver.   That's a very subjective topic but I kept reading rave reviews of the "quiet" receivers in TenTec and Elecraft radios.  I am in no-way an expert on receiver design but TenTec and Elecraft seem to design their receivers differently from the "big brand" radios, and in most cases include front-end filters narrow enough to filter out the noise around a thin CW signal.  There are other niceties like having physical knobs to control keying speed or message sending, etc. without having to enter a menu.  That is standard on most TenTec and Elecraft radios but is normally a menu controlled item on "big brand radios" which makes it hard to change during a QSO.  

You can see where I'm heading here.  My choices were narrowing to TenTec and Elecraft brands (coincidentally, both are American radio companies).   Both companies make QRP radios although Elecraft has more QRP offerings.  Of the current TenTec radios I believe only the Argonaut and Patriots are QRP.  The Argonaut receives very positive reviews but there were not many available used and I didn't want to pay for a new radio so that sent me toward Elecraft.

Elecraft KX3

Most of the Elecraft models are offered as kits.  I'm not competent enough to correctly solder hundreds of components and wind toroids for a radio so I was looking for used pre-built rigs for sale on a major auction site and eham.net classifieds.  Most of the good deals on eham.net classifieds seemed to be quickly snapped up.  I bid on a number of radios on the major auction site but the bids consistently went higher than I was willing to pay.  At first I was bidding on only Elecraft KX1s, then Elecraft K1s, then I moved up in price to Elecraft K2s then to Elecraft KX3s.  I lost all those auctions.  I revisited eham.net classifieds and saw an ad that had just been posted for a KX3 with the options I wanted that was much less than the going price on the auction site.  I sent an email and a week later my KX3 arrived.

The KX3 has been a joy to use.  All the controls I need access to are very accessible without menu diving.  I've made more CW contacts at 5w this past week than I made in all my time with my QRO radios and I made one SSB 10w contact (just to speak with an old acquaintance on the Corn Cob net).   It's internal auto tuner has been able to match my 40m Carolina Windom at 1.0-1 on every band except 160m and 30m.  On 30m it can match at 1.7-1 and 160m it just clicks.  It matches better than my manual MFJ Versa Tuner.

It matches my end-fed dipole 1.1-1 on every band from 40m-6m.  I don't recall trying 80m on that end-fed antenna yet.

The KX3 has internal batteries that I operated at 3watts transmit for a few hours on outside (only a couple of QSOs).  I was operating from my front porch with a 31ft wire thrown up into a tree.  So it's an eminently "Porch Portable" or picnic bench radio.

I have a little 3ah 12v battery left over from a UPS.  I operated with it for a couple of hours and it only dropped from 12.5v to 12.2v when I was done so that's a nice option to have for longer portable operations.  My 50ah UPS battery, while not terribly portable, should allow me to operate off the mains for a week or more! 

The radio, antenna, paddles, and external battery all easily fit in my backpack.  I can't say I could do that with my ICOM 746-pro.

My only limitation on portability presently are my Bencher paddles which weigh twice as much as the radio !!!  But I have a Palm-radio paddle on-order so that should be taken care of shortly.

Bencher Paddles 3lbs 2x the weight of the KX3 radio itself

Elecraft makes a fine radio.  I'd like to operate a TenTec Argonaut some day as well but that will need to wait.

73s and 72s

N4PBQ

First Portable QRP OP

Not exactly roughing it in the wild...

N4PBQ remote station.

So a trip to family in the Western part of the state provided my first opportunity for a portable operation with the Elecraft KX3.  Calling this a "portable operation" is a bit contrived but I was outdoors, battery powered and sitting comfy under an oak tree for a few hours.

 A rope with an lead weight allowed me to get the rope up into an old oak tree.  The weight goes up over a branch and back down.  I untie the weight and attach the antenna and then pull it up to the apex. 

The bottom of the end-fed random wire antenna is connected an 9:1 UnUn to lower the impedance to something the radio's ATU can match.

Operations

No it's not a torture device

More mosquitoes and ticks were biting than contacts but I had a very nice long rag chew with N8NSN.  Turns out he has an incredible station of classic equipment that he's painstakingly restored.  We had a great conversation about options for portable straight keys,  He suggested looking at an Army Leg Mount...

I'm digging it. It has kind of a steam punk vibe.

The radio was powered by a 3ah 12v old battery for a good part of the day.  About an hour of that time was transmitting at 5watts power.  The receive drain of the KX3 is very low with the display turned off (right from a button, no menu required) so a relatively small battery lasts a long time.

It's difficult to see but I'm holding a Palm Radio Single Key Paddle in my left hand while sending with my right.  I simply laid the key down between transmissions.  I'm very happy so far with the Palm Radio Single Key paddle.

Arm chair copy ?

Here's the KX3 in all it's portable glory...
Plugged into the left is power from a small external 12v 3ah battery.  It has more capacity and higher voltage than the internal AA nmih rechargeable batteries.  If I run the external down I can fall back to the internals.  
Connected to the middle plug is the CW key from Palm Radio which is wonderfully portable (AA4XX recommended the key) although I'm getting used to holding it during operation rather than having it attached to a base.
The noise canceling ear-buds are plugged into the bottom jack on the left.
The coax to the antenna is plugged into the BNC on the right of the radio.  The radio has built-in feet to prop it up during operation.  I'm not sure how I'd feel about sitting it directly on the ground.  It has plenty of gaps for insects and debris to get inside.  I think if I operate sitting on the ground I'd set it on my backpack.

Elecraft KX3 portable with Palm Radio Single CW Paddle

So all-in-all the my first portable HF OP was a qualified success.

• I didn't get the antenna stuck in the tree
• I didn't accidentally brain myself with the lead weight on the throwing rope
• I didn't get attacked by killer bees or caught in a sharknado while operating outdoors
• The battery performed beyond my expectations
• My CW key worked very well hand-held
• I made contacts

So lower your power, and raise your expectations.

73 and 72s
Richard
N4PBQ

BLT+ Balanced line tuner at Excalibur

Another portable test of the BLT+ tuner

KX3 operating on internal battery.  What a fantastic portable rig.

I took the BLT+ balanced line tuner out to the Excalibur antenna site to try it out on the doublet antenna that we put up last Saturday.  This was the first test of that antenna (40m and 80m using a common feedpoint).

I didn't have much time today and after the first QSO it started to rain so I packed up and left before getting as much documented as I would have liked.  I apologize for not recording the actual tuning process and the subsequent QSO.

BLT+ connected to open wire line (under the gloves) going to ta 40m Doublet at 65ft

I had the KX3 operating using its internal batteries and outputting 2w. I was running 2 watts because that is the most efficient PA mode for the KX3.

I used the BLT+ to tune the 40m/80m doublet.  Balanced line antennas perform better with a tuner designed for balanced line and this was a good test for both the tuner and the new antenna. 

Portable shack, courtesy of three plastic chairs

I quickly matched the doublet using the BLT+ using the lowest impedance setting which is also the most efficient.  I was glad to see that the BLT SWR LED indicator is bright enough to be seen in direct sunlight.  I was wondering about that but you can definitely tell when it dims even in direct sunlight.

Performance

After quickly tuning up I sent my call two times and was promptly answered.  The other station was running a Flex 6500 into a KPA500 and a OCF Windom at 50 feet. 

He reported me as 559, while he was a 599.  He was running a new KPA500 amp at 500w so we were a bit mismatched on power.  

Interestingly the difference in 2w and 500w exactly matches the 4 S-Unit difference in our reports if you do the math (each increase in an S-unit requires quadruple the power). 

AA4OO sitting back and listening to the QSO

Paul AA4XX kindly snapped some pictures while I was listening to the other operator.  This is the Excalibur antenna site but the shack is outside the photo. 

The Doublet's feed line has not been brought to the shack yet so I was just sitting under the antenna.  The open feed line is running along the ground for a bit which certainly didn't help the signal but we haven't installed the posts to carry the feed line over to the shack and I was too lazy to move the chairs far enough away to keep the feed line in the air.

In the foreground is some saw-grass common on the NC coast.  I'm not sure why it's growing this far inland.

Portable shack at the Excalibur antenna site... The Doublet is 65 feet above my head

Waiting my turn in the QSO... holding the Palm Single Paddle.  BLT+ tuner in the chair to the right

Video

Here is a brief video showing how the BLT+ is connected to the Doublet...

Summary

The little BLT+ performed great with both balanced line antennas I've tried.  It is easy to use and allows me to use my KX3 with balanced feed line antennas now.  I encourage you to build the kit from Pacific Antenna / QRPKits.com .

That's all for now

So lower your power and raise your expectations

72/73

Richard, AA4OO

BLT+ Tuner portable Test

A shot in the dark

I wanted to test the BLT+ Tuner portable with a ladder line fed Doublet but my time has been limited.  After getting home from work one night I assembled a 40m Doublet fed by 450 Ohm ladder line in my driveway.

I pushed the Doublet up on my Jacktite pole and attached the ladder line to the BLT+ and attached the BLT to the KX3.  I had the KX3 sitting on the deck table running on internal batteries.

BLT+ tuning the balanced line antenna

By the time I began my test it was quite dark except for the moon.  My headlamp was out of batteries and I was operating by a floodlight up on the eve but I was determined to know how the tuner worked with my portable doublet.

Doublet on Push up pole.  Moon in the background.

40m and 30m tuned up 1.0:1 using the high capacitance setting.  Tuning was fast for each band using the SWR indicator LED.  After tuning on 7030 and sending my call then again on 10110, I tried 14060. Although tuning 14m was a bit touchy it tuned using the low capacitance setting to around 1.5:1 SWR.  After tuning I sent my call on 20m.  Immediately I received a call from K7JHM, a QRP station in Utah (about 1700 miles away).  We exchanged signal reports and station information although copy was a bit rough.  I'd neglected to bring my earbuds out and the speaker on the KX3 is pretty poor.

However, the QRP to contact was a success on a portable antenna, tuned with the BLT+ driven by a rig running on internal double A batteries. 

I didn't try higher bands because it was so late in the evening so I packed it all up declaring success.

Balanced line tuner doing it's job

Tuning 20m was a bit touchy because my total length of one leg of the doublet plus the feedline is too near a 1/2 wavelength on 20m.  I need to add about 7 feet of ladderline to keep it from being near odd 1/8 wavelengths of the bands I want to tune. Or I could add 7 feet to each leg of the antenna.  I will need to do that before the next test.

That's all for now

So lower your power and raise your expectations

72/73

Rich AA4OO

Portable Ops in Comfort

Towable Shack

Working my rolling shack portable station from air-con comfort

We've had a few RV's over the years, but for some reason I've never thought to operate from inside the RV.  I have always tossed a wire over a tree and operated from a picnic table or from my camp chair, as here...

But I thought, "Hey, I have a 12v power supply built-into the RV and the built-in ladder makes a nice solid mount for an antenna mast."

Early try with a military fiberglass pole mast

Now I use a Flagpole Buddy with a 30 foot telescoping mast

Here's a link to the flagpole buddy... link

Our RV has a Converter / Inverter with a spare 25 amp 12v circuit.  I tapped into that and ran a power pole wire to the dinette table.  

The camper had a coax outlet to watch a TV outside the camper... that's obnoxious.  So I cut the cable TV coax and crimped on a UHF connector, and ran that to the dinette table.  I simply attach my coax from outside the camper to cable TV coax adapter to get the antenna connection inside the camper.  Wallah, coax through the wall with no drilling. The cable TV coax run from the dinette to the wall outlet is only a couple feet so it's not really impacting the impedance of the coax run to the antenna.

I've tried a couple of antenna's and have settled on my end-fed 44 foot wire fed with a 9:1 balun and some clip on radials.   I pull the antenna wire through top end of the telescoping mast with kite string, counter-weighted with a heavy sinker.  That keeps the wire taught from the end-fed point up to the top of the mast and out at an angle.

Gone RF fishing with a 30 foot pole and a big sinker.

The Elecraft KX3 and Ten-Tec Eagle will both match a bent spoon with their auto-tuners and have no trouble with the end-fed on 40m and above. 

For a portable key I use my Palm Radio Single paddle.  Either magnetically attached to the steel side of the Eagle or just held with one hand while operating with the KX3.

Palm Radio Single Paddle

On the Eagle the Palm Radio Single magnetically attaches to the side

One thing I find interesting about operating while "camping" (if you call towing a small house to a campground camping) is that I seem to also work a suprising number of other stations that are operating from a campground.

Note the power and antenna connections under the table

The KX3 can stay on the dinette and doesn't take much room.  Keeping the footprint small and the earbuds in, keeps the XYL happy when operating during an outing.

I worked a number of stations on 40m, 30m, 20m and 10m this weekend.  It's always fun to tell a station that you are portable, even if you are essentially operating in your home away from home.

Thats all for now.

Lower your power and raise your expectations

Rich AA4OO HamRadioQRP.com

First Field Day as a CW operator

Field Day 2016 with the Knightlites QRP club

I had the privilege to be part of the Knightlites WQ4RP 2016 Field Day event.  They are a great bunch of folks dedicated to QRP radio.  They operated CW and SSB on 80m, 40m, 20m, 15m, 6m, 2m and 440.

After listening to CW for nearly 19 hours straight; my brain is turning even normal sounds into morse code...  I may have had a psychotic break.  

Gary, N3GO, operating 80m straight through the night without leaving the oh-so-comfortable lawn chair

My 80m/15m station

This is my first year operating CW and my first full, field day event.  I've dabbled in field day (FD) in the past but did not work it as part of a club.

For this FD I was responsible for supplying the equipment to get a station on the air for 80m and 15m.  The WQ4RP club operates QRP only using battery power, so anything associated with transmitting was to be battery powered including the computer.  My Elecraft KX3 was powered by a 12 year old 50ah UPS battery and the laptop was powered using an inverter with a large deep cycle battery.  Following 20 hours of operation the UPS battery had only dropped to 12.2v  The Elecraft KX3 is frugal with power even after hundreds of contacts.

My antenna was the one we'd previously installed at Excalibur during the spring.  Paul brought it down for us to use at the FD site.  We cut the 40m part of the fan dipole to work for 15m. Tall trees on either side of the tent provided the antenna supports and the tent was positioned to be close to the feed point of the ladder line.

80m - 15m Fan dipole with home brew ladder line

Honda generators powered the lights in the evening and fans/AC during the heat of the day. Honda generators are quiet in both the audio and radio spectrums.  Three Knightlite stations used Honda generators to power equipment not related to transceivers.

Power was supplied to all stations by Honda i-series generators

Operating CW during Field Day

Unfortunately for FD operations I'm the opposite end of a CW contester.  Since starting my CW/Morse Code journey last year I've just worked at getting my ragchew (conversations in CW) skills improved.  I practice listening to the most common 500 words and listening to e-books sent as Morse Code.  I'm not good at copying calls, when they are sent at 25wpm.  Compounding my new(ish) operator struggle is that FD uses an abbreviated exchange, so it was tough going for me when operations kicked off at 2PM local time Saturday and the exchanges began flying by...

A Field Day CW exchange

Calling Station sends an abbreviated CQ, sometimes the CQ and the ending FD were omitted:

CQ FD N4HOG N4HOG FD

Answering Station sends call by itself, repeating as necessary:

WQ4RP (repeat call after a brief pause if no response)

Calling Station sends my call back to me then his station class and section:

 WQ4RP 1E NC

Answering Station sends station class and section:

3A NC

Calling Station sends thank you and that's it, you're done:

TU

Since we were operating QRP we often had to repeat our call and our class and sections.  I don't have much experience at copying calls at speeds above 20wpm.  The 15m band was weak and most signals were no better than S2 or S3. I was trying to copy calls sent at speeds higher than my norm with QSB (fading) and I was getting frustrated.  Paul came and sat beside me to coach and provide some encouragement.  He is a patient tutor.

I was advised to operate "search and pounce" rather than sending CQ myself because I needed to hear a caller complete a QSO once or twice to copy their call and their response but even then copying the section was often harder for me than the call.  Many of the sections are 3 letter designations that I was unfamiliar with (i.e. California has 10 sections abbreviations).  Between QSOs Paul would explain where each of the sections were located. I should have studied up on this stuff prior to FD.

I'd hear the station class (a number and a letter) and then while my brain was chewing on that I'd miss the section.  So I was sending a lot of AGN? to get the stations to repeat their response. Sometimes I'd finish a contact and realize I'd mistyped part of the response so I would wait and listen for the caller to go through another contact to hear what they sent to copy it correctly for the log. I wasn't really racking up the contacts.

This type of operating is very challenging for me.  While I can understand why contesters enjoy honing these skills, for me, it was stressful and wore me down mentally.  I took breaks at least every hour and asked other, more seasoned operators to take the helm (errr. key) while my brain cooled down.

80m magic

When dusk arrived 15m contacts were few and far between and I switched to 80m.  Gone were the weak signals and speed demons on 15m.  The 80m band was surprisingly QRN free and stations sending FD calls were stacked like firewood throughout the CW portion of the band.  Our QRP station was also heard better by the callers with fewer needs to repeat the call or the response.  I had more enjoyable time working 80m.  Paul still sat with me and offered advice which I greatly appreciated.

Gary N3GO, loves the 80m band and he is the Knightlites anchor man for running 80m through the night.  Gary sat down at 10PM to begin his shift on 80m and he didn't get out of that chair until 5AM.  I was dozing on and off (more off than on) in the tent and doing my best to head copy what he was working.  Seven straight non-stop hours of CW later Gary needed a break and I spelled him for a while.  After a bit of rest he was back for more and operated until the band gave out in the morning.

N3GO is the anchor man for 80m through the night shift

WQ4RP Knightlites

The Knightlites operate using the club call WQ4RP.  Here are some of the participants from the 2016 FD.

Left to right: AA4OO, WA4GIR, WF4I, (visiting ham in red ????), KD4PBJ, KC4PHJ, AA4XX, AB4PP
Thanks to W4MPS for taking the photo

Photos

"JP" AB4PP -- 20m Band captain

 Kurt N4KJK - assisted with 15m CW

6m / 2m / 440 stack - Thanks Alex!

Alex KC4PHJ -- Band captain for 6m / 2m / 440

Joe WA4GIR - 40m band captain

40m Station

40m Loop

Derek WF4I - working 40m at dawn

Sunday daybreak and the 80m station is still cranking

Lots of weed eater support lines tied off at the base of this tree

Summary

My first FD as a CW operator was challenging but fun,  The WQ4RP club has some patient and talented operators, many of whom have rarely missed operating a FD since becoming hams.  I enjoyed getting to learn from them.

Next year I will make the effort to practice copying FD exchanges prior to the event so that I'm not so overwhelmed.  It also turned out I'd made a poor choice for logging software.  The RumNLog software for my Mac laptop didn't have a preset for the FD contest.  I had to use a general contest setting and now will have to programmatically manipulate the resulting ADIF output to have the necessary fields for submission.

The Elecraft KX3 is unsurprisingly a good QRP field day radio.  It's small size, low power consumption and phenomenal internal auto tuner made it a pleasure to work with.  It has a knob, button or display element for everything you could want.  For instance, the dedicated knob for changing internal keyer speed was very useful to fit each station we worked during an exchange.  I also used the secondary frequency display area to check on the power supply voltage throughout the event.  The KX3 truly does have the kitchen sink.

Update 7-11-2016

Paul sent me the Knightlites field day results. Lists below.  I'm interested to see how our group fared .

Call Used: WQ4RP     GOTA Station Call: (none)     ARRL/RAC Section: NC     Class: 3A

Participants: 10     Club/Group Name: KnightLites QRP Society

Power Source(s): Battery

Power Multiplier: 5X

Bonus Points:
  100% Emergency power                            300
  W1AW Field Day Message                          100
  Submitted via the Web                            50
Total Bonus Points                                450

Score Summary:
                  CW  Digital  Phone  Total
   Total QSOs    539      0      58
 Total Points   1078      0      58   1136   Claimed Score = 5,680

That's all for now

So lower your power and raise your expectations

72/73

Richard, AA4OO

TEN-TEC Century 21 --- Vintage Novice CW Rig

TEN-TEC Century 21

A second HF rig has somehow found its way into my home.

Ten-Tec Century / 21 CW Only Transceiver

Since getting back into HAM radio with my focus now on CW and QRP I find that many of my contacts use old and/or homebrew equipment.  Maybe it's because I often call CQ with my straight key rather than paddles that results in most answers to my CQ being operators using a straight key or a bug.   It seems these operators tend to not use the latest piece of shiny gear, which made me an anomaly; sending with a straight key while using my SDR-in-a-box like the Elecraft KX3.  Maybe for this reason I've found myself being drawn to less sophisticated types of equipment.  I'm not talking about wanting to go back to spark gap and gravity batteries, but sometimes the KX3 is just too easy to use.

In the same way that I'd prefer to send CW using a Straight Key to a keyboard since it's a greater challenge, I think that the older, less sophisticated equipment can bring more satisfaction to the hobby.

Vintage... like bell bottom jeans and corduroys 

Now don't get me wrong, I'm not suggesting that the only "real" radios are those with discreet components or tubes, nor am I saying no key but a straight key.  I'm just moving through some stages of the hobby that I missed because I didn't grow up with this older equipment and I think the challenges can be fun to learn and operate.  

I didn't get into Ham radio until 2006 and the commonly available used equipment of the time was microprocessor controlled rigs with digital displays, optical encoders, DSP filters and seemingly endless menus for configuration.  I went through a few HF radios over a couple of years: a Yaesu FT-857, ICOM 730 and lastly, a ICOM 746 Pro, before I sold the radios and dropped out of the hobby. At the time none of those rigs held any "magic" for me, they were just tools with increasing levels of functionality and ease of use.   However the ICOM 730 did hold copious amounts of stale cigarette smoke and nicotine from the previous operator that it would release into my room as it warmed up.  Not really magic, more of a non-corporeal element let's say.

If you've read my earlier posts you may recall that although I like my Elecraft KX3 immensely I have some strange fondness for TEN-TEC equipment.  Ten-Tec has made some quirky radios with legendary full break-in QSK and supposedly smooth, quiet receivers for CW operators for a few decades now.  So when a Craigslist posting leaped into my browser window (I don't know how that happened) advertising a seemingly pristine late-70s rig that had supposedly been reworked to a perfection, all for $140, I just couldn't pass it up... well at least the price in the ad was accurate.

The Ten-Tec Century 21 is an interesting transceiver.  In the simplest sense it was an ideal radio for the Novice Licensed HAM operator of the 1970s.  It is a CW only transmitter.  It doesn't require fiddling with a resonant tank circuit of the typical tube radios of the era to work out resonance.  It has a built-in power supply that runs off 115-120v mains.  It doesn't use a superheterodyne receiver but a direct conversion receiver (Ten-Tec called it a double direct conversion receiver).  This resulted in a simplified design and good selectivity but without the IF there is no AGC so be ready to work those RF/AF gain knobs.  It also has easy band changing and nice filtering.  From web searches and reviews its most common problem is a PTO that has to be rebuilt every few years.  The Ham I purchased mine from said it had been rebuilt.  It doesn't slip (yet) but it's kinda stiff so I expect a PTO rebuild to be in my future.  I spoke with a ham I work with who has rebuilt one and he said it's not difficult, simply time consuming (but he repairs electronics all day so YMMV).

Operation is relatively simple:  

1. Start with the radio off.
2. Turn the Drive knob down (counter clockwise), select your band 
3. Turn the radio on by pushing in the RF Gain knob (it is the on-off switch).
4. Find and open frequency (wait, listen, wait again, listen) and while holding the Set Drive button apply just enough power using the Drive knob to give you some RF out for matching your antenna.  Better yet use a frequency analyzer to tune QRM free.
5. After you're matched up you can bring the power up to where you want to operate.  Unfortunately this can't necessarily be done into a dummy load unless you're match is near 1:1.  The SWR will affect how much output drive you can use.  If you're going to run QRP then no worries because you won't be running the power input up to a point that could trip the final, Maximum input power is marked by the thick line on the Input Power meter (about 70w).  This results in differing output wattage dependent on antenna resistance and frequency.  I found that into a 50ohm dummy load I could generate up to 40w output for 80m, 35w output for 40m, 30w output for 20m and so on, down to about 15w output on 10m.  As I plan to use the rig for QRP this is mostly academic.  It certainly can provide more than QRP output levels if conditions warrant.

To Tune a Station prior to the QSO

This seems more complicated than it should be but I'm guessing after I've done it a few dozen times it will become automatic.  

The Offset Knob

The CW tone you hear is the difference between the current PTO tuning and the position of the Offset knob.  The Offset knob can be an offset to either side of the current frequency (think of this as CWR depending on your band).  In other words the zero position of the Offset knob applies zero audio offset to the currently tuned frequency so you wouldn't hear a tone from a signal with zero offset.  You should have the Offset knob slightly to the left on 80m and 40m (LSB offset) and slightly to the right of zero for the USB bands.

The Zero Beat Knob

So with the information above in mind... Pressing the Zero Beat button defeats whatever the Offset knob is set to (effectively zeroing the offset).  When you are exactly on frequency with a signal the audio from the signal nulls (goes silent).  This null / silence is your indication that your transmitter frequency matches the other station.  

However I've found that the Null or Zero Beat is quite broad, such that you could be up to 250Hz off frequency based on where you leave the PTO in the Null. 

For my radio, on LSB bands, I press the Zero Beat button, find the null and then go past it (turning the knob to the left) and then just tweak it back into the null.  At least for my radio that works.  Maybe other Century 21s have a finer Q on the Null.  

After you have zero beat the signal you can use the Offset knob like a RIT. The range on that knob is really broad.  I think the manual said 5kHz so just a touch goes a long way unless you like to listen to CW with a ear piercing 2kHz, high pitched tone.

Here's a video demonstrating operating the rig...

TEN-TEC Century 21 -- Front Panel Controls

QSK

The Century 21 has full break-in QSK on at all times.  It is extremely clean with no discernable pops or artifacts.  One complaint I have is that the pitch and tone of the sidetone itself is fixed.  You can vary the volume through a little hole in the bottom cover to turn a thumb wheel, from very loud to just loud but you cannot change the pitch and it's a bit harsh sounding. 

The headphone jack on my particular radio is broken.  I need to open it up to resolve that before the wife uses a large heavy object on my beautiful new transceiver.

Selectivity

This video demonstrates the receiver selectivity of this old radio. 

Where is the S-Meter?

This is a bare bones transceiver with just the basics necessary for CW communication.  As far as information for the operator: Well there's an analog dial that gives you a rough indication (within 5kHz) of where you are transmitting, and an input wattage gauge for the drive and that's all.  Notably missing is a Signal Strength meter so the signal reports you send will be based on your ear, or how generous you're feeling at the time.

It's a little funny to me that I'm enjoying using this radio given it's lack of... well just about everything compared to my Elecraft KX3 whose tiny display indicates Signal Strength, Signal Relative to Zero Beat, SWR, RIT Offset, VFO A/B (down to a 10Hz range) Time, PA Temp, etc.  It just goes to show you how much modern rigs have that, when it comes down to it, isn't actually necessary for communication.

Specifications

A bit of history about TenTec QRP radios and the C21 from a 1977 magazing article...

https://archive.org/stream/73-magazine-1977-12/12_December_1977#page/n29/mode/2up

General

• Frequency Coverage: 3.5 to 4.0; 7.0 to 7.5; 14.0 to 14.5; 21.0 to 21.5; 28.0 to 28.5; 28.5 to 29.0 MHz. (Crystal not supplied for 28.5 to 29.0 MHz, but available as accessory, Model 273.) Note - Early models only included crystals for 3.5, 7, and 14 MHz bands. Crystals for 21 Mhz and 28 Mhz bands were available as optional Models numbers 271 and 272.
• VFO Frequency Stability: less than 20 Hz change per degree Fahrenheit, averaged over a 40^o change from 70^o to 110^o, after 30 minute warmup. Less than 20 Hz change from 105 to 125 VAC line voltage.
• Direct Frequency Readout: Marked in 5 kHz increments from 0 - 500 kHz, MHz markings for each band displayed.
• Tuning Rate: Approximately 17 kHz per revolution of main tuning knob.
• Power Requirements: 105 - 125 VAC, 50-60 Hz. 10 watts receive, 100 watts transmit.
• Semiconductors: 25 transistors, 26 diodes, 5 integrated circuits.
• PC Boards: 4 plug-in types, 6 integral.
• Construction: Rigid aluminum chassis and sub-panels. Aluminum case. Grey front panel, black textured vinyl cover.
• Dimensions: HWD 6.125" x 12.5" x 12"
• Weight: 15.5 lbs

Receiver

• Sensitivity: 1 uV or less for 10 dB S+N/N.
• Selectivity: Three position; 0.5, 1.0, and 2.5 kHz.
• VFO Frequency: 5.0 to 5.5 MHz. Double Direct Conversion.
• Antenna Input: 50 ohms, unbalanced.
• Audio Output: 1 watt @ 8 ohms, less than 2% harmonic distortion. Built-in speaker; PHONES jack.
• Offset Tuning: Approximately +/- 5 kHz, defeatable with ZERO BEAT switch.

Transmitter

• DC Input Power: 70 watts
• RF Output Power: 25-30 watts, typical.
• Output Impedance: 50 - 75 ohms, unbalanced.
• T/R Switching: Full break-in cw with PIN diode switch.

QSO

Sample QSO... Listen to the lovely receiver but the horrible sidetone.

Update: Here's another QSO I made a few months later into learning the Code.

And here's yet another from Straight Key Night 2017.

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Some of this old beauty's insides...

As I use the rig more I'll try to make some recordings and post them in subsequent blogs but that's all for now.

So lower your power and raise your expectations

73 / 72

Richard

AA4OO (formerly N4PBQ)