[TMC] TMC and AM?

[H A Layer]

Hi Eugene:

Just spotted your question regarding TMC AM.  My TMC rig was the PAL-500 
and the GPE-1.  Loved it.

The GPE-1A is a great little AM exciter for TMC linears.  It has a 
balanced 600-Ohm audio input as well as a
carbon mike input and a Hi-Z mike input --all three available by means 
of a front panel switch.
The layout is generous--not crowded--much easier to service than the SBE 
exciter.  I highly recommend it.

K4OZY's PDF file of its manual: 
http://www.virhistory.com/tmc/tmc_pages/tmc_manuals/manuals_db/gpe/tm_gpe-1a_10_1_63.pdf

73 Hal KK6HY


On 3/2/14, 12:55 PM, W2HX wrote:
> Thanks, John.  So I guess I will keep an eye out for a GPE-1.  I don't run much AM, but when I do, it would be nice to run some TMC equipment.  I do occasionally check into a burgeoning AM net using military gear up here on the east coast, so it might be fun. Other than a central electronics 100V and 200V, the only other AM I have is really AME.
>
> thanks for all of the info. Seems a lot of TMC gear has found homes in recent years and the liquidity of circulation seems to have waned. IF anyone on the list has a GPE-1 they would like to part with, please let me know.
>
> thanks again everyone.
> Eugene
>
>
> -----Original Message-----
> From: tmc-bounces at mailman.qth.net [mailto:tmc-bounces at mailman.qth.net] On Behalf Of John Vendely
> Sent: Sunday, March 02, 2014 2:04 PM
> To: tmc at mailman.qth.net
> Subject: Re: [TMC] TMC and AM?
>
> Hi Eugene,
>
> TMC made a plate modulated, 1W AM/CW/MCW exciter, the Model GPE-1, which will work directly with your PMO, and is ideal for driving any of the TMC linear power amps.  You can get 125W of very good AM with your
> PAL-500 this way.  This is what TMC originally supplied to customers who still used AM, and I think this is your best bet.
>
> Among their sideband exciters, the TMC MMX-2 series solid state exciters are best suited for AM, as they have a separate AM modulator in addition to the ISB modulator.  However, relatively few were made compared to the SBE and SBG series, so they're kinda scarce.  And there are other serious difficulties with the MMX-2 because of their complicated direct analog synthesizer.  These things are invariably all screwed up when you get them, are very tricky to get working, and can have spur problems requiring fairly regular tweaking.  They weren't a terribly successful product line, but when they're working, they're very good exciters, with top notch audio quality on both SSB and AM.
>
> Frankly, I've never quite understood all the current fuss over AM, and don't operate AM too often.  Despite all the obsessing over audio quality, AM usually sounds horrible, due to selective fading problems, particularly during even shallow carrier fades.  There-- I've said it, and now I'll descend from the soapbox.  I confess I do run AM occasionally, and then I use either the GPE-1A, MMXM-2, or an SBG-1A exciter with an external AM modulator.
>
> The SBG-1A frequency synthesized exciters have essentially the same sideband modulator as the SBE, but in a separate chassis (Model CBE) together with the sideband monitor.  The CBE sends the 250 kc ISB signal to the "Frequency Amplifier" (Model CHG), which upconverts it to the operating frequency.  For AM, I just disconnect the CBE sideband drive to the CHG, and feed in my own high linearity 250 kc amplitude modulator.  The rest of the system operates in the normal fashion.
>
> An old buddy of mine devised still another solution many years ago.  He added a small plate/screen modulator to the 6146 output stage of an
> SBE-3 exciter.  A small modulation transformer which he improvised was mounted inside on the rear apron of the exciter, and provided an 8 ohm input impedance for a small external audio amplifier.  Any small hi-fi amp that will deliver a good clean 5W will do fine.  He used one channel
> of a Dynaco SCA-35.   In retrospect, he considers the mod a debauchery,
> but it worked great.
>
> I hope these suggestions prove useful.  Have fun.
>
> 73, John K9WT
>
> On 3/2/2014 12:08 PM, W2HX wrote:
>> So all this discussion about the SBE not being well suited for AM.  So I have a PAL-500 and would like to run AM through it. Can anyone recommend a TMC exciter that will do good AM and will work with the PAL? And something that has a VFO or can use my PMO-5. And more importantly, does anyone have such an animal for sale?
>>
>> thanks
>>
>> 73 Eugene W2HX
>>
>>
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