[Milsurplus] GP-7 transmitter

[W2HX]

Silly question on my part. Other than a fan that might be expecting AC, the filaments and B+ are DC, right? So why not create an outboard power supply to generate 2000 VDC and whatever else it needs? Sure there will be some iron and rectifiers and big caps, but isnt that doable? Or is that just as much, or more, work than finding a source of 800 Hz? (maybe that is the best answer afterall).

I've also seen some Elgar AC supplies, some have variable oscillators. I don't know if these can go up to 800 Hz or max out at 400 Hz, I'd have to look into it further.

Anyone know how many watts need to be supplied by such a supply?

thanks all,
73 Eugene W2HX

________________________________________
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> on behalf of Michael Hanz <aaf-radio-1 at aafradio.org>
Sent: Thursday, February 28, 2019 10:36 AM
To: Jack Antonio; milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] GP-7 transmitter

That's an excellent rundown, Jack.  I would only add that there is a
pesky little 800~ centrifugal fan under that chassis to cool the 803
that has to be considered when deciding to use something other than an
800Hz 115vac supply.  As you know, despite the weight (and an 800-1
inverter isn't exactly lightweight), I like the Behlman laboratory AC
supplies for this and the GO transmitter.  They are quiet and reliable.
The older ones with analog meters can occasionally be found reasonably
with a patient search, and Behlman is pretty good about emailing pdf
manuals for the older equipment, or they were the last time I called them.

- Mike  KC4TOS

On 2/28/2019 5:32 AM, Jack Antonio wrote:

> On 2/27/2019 9:21 PM, W2HX wrote:
>> I recently ran across a photo of one of these transmitters and it
>> piqued by interest. What are your opinions of this transmitter? How
>> would you compare it to, say, a TCS transmitter or a ATD
>> (disregarding the multi channel capability) or even the BC-375?
>
> If you like operating a BC-375 or ATD, you will feel right at home with
> a GP-7. Like the BC-375, the complete set of tuning units will take up
> a lot of space. There is no provision on the transmitter for a local
> microphone or key, and on/off control, those functions are provided by
> the remote control boxes. There are two, the pilots and operators
> boxes. The operators box provides the connections for sidetone to
> an external receiver. The two boxes together with the transmitter
> provide an interphone function. (Think pilot/gunner in an SBD).
>
> At least one of the tubes (801) is an audiophile type tube, the
> 843 may also be an audiophile tube, as it is a directly
> heated triode.
>
>> I​'ve read it used 800 Hz power? Do hams build their own LV and HV
>> power supplies for this?
>
> Providing power is the biggest stumbling block.
>
> Building an external supply would require extensive modification.
> High B+ is 2000V, plus multiple low voltage filament sources.
>
> Providing 120V 800cycle takes effort. A rotary inverter takes
> a substantial amount of DC power, and is acoustically noisy.
>
> There are static AC power sources that run from 120V 60 cycle, these
> are heavy, and can be a bit expensive, even on the used market.
> Relatively inexpensive units do show up on eBay, but you have to keep
> an eye out for them. In my case, I found a pair, in not quite the best
> of shape, and making one good unit out of the two. They came from
> Texas, so freight wasn't too bad.
>
> I tried a PE-206 inverter, but it is an 80V unit, and required
> a 400 cycle variac to get up to 120. It was OK for phone, but wasn't
> capable of running full power CW, and was a bit chirpy due to
> voltage regulation.
>
> I was always a dollar short and a day late for a 120V 800 cycle
> inverter, so can't comment on how well that works.
>
> Also, there is a motor/generator set out there(not intended specifically
> for the GP)that runs from 120V 60cycle, but it is very large and heavy
> and probably not too common.
>
>> Stability? Ease of maintenance? ease of use? fun to use? etc? I am
>> not sure I want to add one to the collection but it really has caught
>> my eye.
>
> Again, I rank the GP-7 on a par with the BC-375 as far as usage goes. My
> unit has survived all my experiments with powering it, so I have to say
> it is reliable. My GP-7 came to me pretty clean, the only issue I had
> with the transmitter itself was a bad 803. My ATD, on the other hand,
> was a very different story.
>
> One last thing, when looking for GP parts and pieces, there were earlier
> versions of the GP, that weren't exactly the same. They use different
> tuning units, they look the same but don't interchange. I know the
> GP-3 and 4 are different from the GP-6 and 7, but when the
> change occurred, I'm not sure.
>
> Anyone have a manual for a GP-3?
>
> Jack Antonio
> WA7DIA
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--
Michael Hanz - KC4TOS

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