CE 20A on AM?

[kd7oan]

Just a newbie wondering if anyone played with a central Electronics 20a on AM? I have one I was thinking about getting on the air. Also have a knight T-60 I'm toying with. Either one better than the other for this quest?  So far the CE is only working in CW mode so I have some work to do to it.... Or perhaps alot....

Bob R.
kd7oan

[wa2dtw]

Hi Bob
I used a Central Electronics 20A exciter many years ago, when a child.  It worked on every mode imaginable, including CW, AM, FM, PM, SSB, etc.  It was fun to watch the electric eye open and close while I was speaking.  It worked fine on AM.  You do need a linear.  Used a rewired Globe King 400B (biased for class AB1) as a linear. 

If you want to go on SSB, you will need a 5 mc VFO.  (I used a converted ARC5 for that).  These were the days when AM ruled supreme and SSB was only seen rarely, on the top part of 75 meters, and even more rarely on 20M.
73
Steve WA2DTW

[WQ9E]

Hi Bob,

The CE-20A will work fine on AM but as previously posted the power output is fairly low so an amplifier will be very helpful.

Note that some varieties of the 6AG7 output tube do not like working in the horizontal position so be careful how you orient the chassis while doing alignment to avoid damage to the tubes.  The position is only important while they are powered on.

If you haven't done so, download the 20A changes manual from the Bama website: (often the Edebris mirror site works better so also try:  http://bama.edebris.com/manuals/ce/20a/  ) and consider making any updates that your 20A does not have.

The main alignment procedure in the 20A manual calls for the use of a scope however most people will find that it is easier to do the alignment with a selective SSB receiver.  The problem is that it is sometimes difficult to interpret the scope pattern if you end up with a mixture of hum, some distortion in the audio chain, poor carrier, and/or poor sideband suppression.  Using an external receiver you can listen as you balance the carrier and adjust for best unwanted sideband suppression.  I use a spectrum analyzer plug-in for my Tektronix scope so it makes setup pretty easy.  It is possible to achieve very good suppression for one sideband at the expense of lowered suppression for the other.  This is not really important if you are only using the CE for CW and AM but if you do decide to operate SSB with it and only plan to use it on 40/80 or 10-20 meters then you can optimize the adjustments for either LSB or USB.

The relays are becoming problematic in these units, many CE products use a "telephone type" relay with a high resistance coil that opens up over time.  You can find replacement coils on the internet at very high price or if necessary you can still buy modern DC relays from Mouser and others that have a high resistance coil.  This is definitely a better option than letting the exciter sit on a shelf for lack of a good relay so keep this in mind if your relay does go out.

Have fun with the CE-20A, it is a neat little transmitter/exciter.  I have mine paired with an RME-4350 receiver along with the matching CE VFO and "sideband slicer".

73, Rodger WQ9E

[nq5t]

Some applause to CE for generally making every mode known to the mid 20th-century ham available on their radios.  I've tried my 100V on AM a few times, and it plays pretty well although a bit PW without an amp.

On the relays, Nick Tusa (http://www.tusaconsulting.com) has new coils for the 10/20 and 100/200 series transmitters (all the same coil) - $65.  I have one, safely put away for a rainy day.

Grant/NQ5T

[kd7oan]

Thanks to all for the input!
I played with it a bit today and it seems to be stuck sending a CW tone. Voice activation works but it sends a tone instead of modulation. Hosed a few things with tuner spray. Relay appeared to be working but how well I'm not shure.  (funky looking thing) I'm better at antenna building than radio repair. Guess I'll get the manual out and see what kinda trouble I can get into with it.... Fun Fun Fun
73'
Bob R. kd7oan

[W2JBL]

i used a 20A with factory modded ARC5 VFO on AM and SSB for many years- mid 70's late 80's. it was also one of my best ever ESSB rigs. the speech amp modifies easily, the only bottleneck being the audio output transformers, which i shunt fed through chokes and oil caps to get the DC off the primaries, which don't handle DC well. kind of like modified Heising. the resulting AM was world calss, and the ESSB (waaaay back in 1976!) would put most DSP rigs to shame in this era. never had a relay problem, and the VOX was outstanding. only complaint was dirty mixers and instability on the higher bands. for 160, 75 or 40 into a clean amp it's a winner. used with a DDS VFO kit it would shine on all bands and i'm tempted to get another one to do just that.