The AM Forum

I'm looking for suggestions for a simple solid state exciter of about 5-10 watts. It needs a VFO - and a CW carrier is all that's required.  160-40M.     A 5 watt VFO, essentially.

Is there a PB board unit like this out there?  I want something small.

I need it to drive my 4X1 plate modulated AM rig.  The 4X1 has an IPA, so 5 watts is all I need.  My FT-1000D works FB as an exciter, but it has a double carrier up 2kc when on 3875. (3875 and 3877)    This is a 1000D synth factory bug and not curable. 

There must be a little kit or hobby unit out there. I suppose I could get a little mobile Yaesu or Kenwood POS, but just wanted to check around for something else first.

T

This will give you the VFO part.

http://www.pongrance.com

Pretty slick, Steve.   Tnx, OM.

If I can find a suitable 160M - 40M  board to do  250MV in and 5-10w out, I think I'll give it a go.



Here's what they say about the output of the VFO:

"Output: The output signal is not amplified, and the level is approx. 250mV peak to peak
which works well with SA612 or similar mixers. Output impedance is 200 ohms. It does
not need to be matched, but the output filter is flatter if the output is matched. With
vintage radios, or other applications, you may need a separate buffer amplifier."


T

There is a buffer amp design on that page. It's low power but made for 50 Ohms.

For simplicity, Tom, I used a TS-50 or even an old rice box POS for an exciter, when I had the "big rig" (4CX1500A plate modulated by a pair of 4CX1200A7's).
Needed 15W drive and the "exciter" never flinched or complained.
Only if you're in a hurry to get your TX on the air.
Fred

ah so Dr. Vu ....

are you still seeking extreme spectral purity ?     purity of essence     essence of purity  ???


this is not so strange as it might seem ....

Tom,

   There is always the vacuum tube exciter possibility. The image posted is from the RCA VFO, a very stable two tube exciter that covers all the bands. See link:

http://69.36.164.11/tube/man/rcagfat42.pdf

Pages 52 to 56

Using an 802 oscillator followed by an 807 would be way cool. Then if you want better stability, add the X-Lock 3.0 like I did to my Knight Kit V44 tube VFO:

http://www.cumbriadesigns.co.uk/x-lock_solutions.htm

My V44 stabilized solution is on the list...It holds the VFO, which is a keyed VFO (frequency shifted) to within a few Hz.

Jim
WD5JKO

JimJim and Tom...I have one of these RCA VFOs....Until now I didn't know it was a commercial unit built by RCA...It looks like a well built homebrew...It is very stable after warmup and I use it to drive my TESLA 360...

That RCA VFO is a beautiful piece of gear.  I have never seen one before (and probably never will in person).

Tom...
How about using the above-referenced digital VFO with the PennyWhistle amplifier that TAPR offers for the HPSDR goodies. 
     http://www.tapr.org/kits_pw.html     
It will make more than enough power when driven to full strap, but those devices are very clean...mid 40s imd...  when run in the 5 or 6 watt range, not that imd makes a whole lot of difference in driving a class C stage.  It's a cunnin' little mini brick...good from 160 to 6m.  You might want to follow it with a switched W3NQN-style bandpass filter if the AM rig doesn't already have a tuned input.

Yes, that RCA VFO certainly is a nice looking and stable unit - especially for tubes  with 25w out.   They are probably very rare.

The HPSDR Penny Whistle is another idea, coupled with the DDS VFO.  I already have the full HPSDR transmitter and receiver working here.... mainly use it as a spec analyzer for now.

Then again, the little Kenwood TS-50 is a possibility.... easy as pie and cheap.

Nice work on the V44, Jim.

Still thinking.   Tnx for the suggestions, guys.

T

And Tom,

Have one of those DDS VFOs here,  and while doing house renovation projects,  had been wondering about using an IXD-414 (or 614 - is that the new P/N?) as the output stage for that VFO.

Probably would need a LPF/BPF following it ...  but ...  It may not have quite enough output.  Perhaps that Gull-Winged part,  the # of which escapes me just now(?).
EDIT  Those higher power devices are the DEIC-420,  and now the 421:
http://datasheet.elcodis.com/pdf2/88/51/885175/evic420.pdf

AND,  Jim,  thanks for the link to the RCA publication.  Had not seen that before.

Realize that the IXD/DEIC parts are not in keeping with tubes,  but would match the DDS approach well.

FWIW,  Vic