[Amps] Glass tube plate color answers

Sun Aug 15 14:29:54 PDT 2010

On 8/15/2010 1:47 PM, Fuqua, Bill L wrote:
> These tubes were run very hot and did not last long in radar or radar jamming applications. I can't get to my tube data but I believe these ran orange at full power and maybe even hotter.
When I ran a single 6C21 (RADAR pulse modulator with a 600 watt plate  
IIRC) I ran the legal limit (then). The first time I tested it, I didn't 
realize the gain even though it wasn't high. I said hello test and blew 
the side right out of the plate.  Checked the bias, plugged in a new 
tube, and "gently eased the mike gain off the lower stop. Even swamped 
grid the thing took very little driving power.  At a KW in and even 50% 
efficiency it ran quite a lot of color.  I've forgotten the plate 
voltage, but it left the 800MA plate meter pegged. I had to take it 
apart to release the pointer, but it worked OK after that.

I did get some reasonably good reports, but the ham down the street 
(bout a city block away) joked, he couldn't operate on 40 when I was on 
the band. Part of that was the amp and part was the receivers we had in 
those days did not exactly have a wide dynamic range.

It was at that point I built up a pair of 813's.  They'd just get a dull 
red, and he could operate on the same band as I did, although still not 
close together

73

Roger (K8RI)
> 73
> Bill wa4lav
>
> ________________________________________
> From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of Charles Harpole [k4vud at hotmail.com]
> Sent: Sunday, August 15, 2010 1:32 PM
> To: amps at contesting.com
> Subject: Re: [Amps] Glass tube plate color answers
>
> Two answers:
> 1.  Glass tubes are supposed to glow very red hot while putting out big RF for us.  If they are not within 1% of burning out, why have them?*
>
> 2.  What happens "When you swap positions"  asked below, is that the other person gets to be on top.  Sometimes this is even fun.
>
> *Same reasoning as, "if it hasnt fallen down, it was not high enuf nor big enuf."   Amps, Antennas and hams need to live large or stay in their mouse holes.
>
> Charles Harpole k4vud at hotmail.com
>
>
>
>> From: wlfuqu00 at uky.edu
>> To: barrie at centric.net; amps at contesting.com
>> Date: Sun, 15 Aug 2010 13:10:42 -0400
>> Subject: Re: [Amps] Glass tube plate color
>>
>> These tubes were never intended to be used as amplifier but in stripline oscillators, either single tube or push-pull.
>> There were no real efforts to match them. In oscillators you want low mu so that they will draw lots of plate current to
>> get started quickly. I seem to recall the plate dissipation was 200 Watts with a very bright glow. These tubes were driven hard is early
>> radar and radar jammers. Often pulsed. Hams used to use them because they were very cheap on the surplus market.
>> EIMAC even made a version with a glass tube attached to it (about 1/2" ID) and no vacuum inside to be used as a ion vacuum guage tube.
>>
>> 73
>> Bill
>> ________________________________________
>> From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of Barrie Smith [barrie at centric.net]
>> Sent: Sunday, August 15, 2010 12:52 PM
>> To: amps at contesting.com
>> Subject: Re: [Amps] Glass tube plate color
>>
>> Damit, Carl, that's a good question! I'll try that right away.
>>
>> Barrie
>>
>> ----- Original Message -----
>> From: "Carl"<km1h at jeremy.mv.com>
>> To: "Barrie Smith"<barrie at centric.net>;<amps at contesting.com>
>> Sent: Sunday, August 15, 2010 10:45 AM
>> Subject: Re: [Amps] Glass tube plate color
>>
>>
>>> What happens when you swap positions?
>>>
>>> Carl
>>>
>>>
>>> ----- Original Message -----
>>> From: "Barrie Smith"<barrie at centric.net>
>>> To:<amps at contesting.com>
>>> Sent: Sunday, August 15, 2010 11:55 AM
>>> Subject: [Amps] Glass tube plate color
>>>
>>>
>>>> Speaking of class C, I have just completed a nostalgia rig using a
>>>> push-pull pair of VT-127As (somewhat similar to the 100TL, but looks like
>>>> a spaceman with grid and plate pins sticking out the sides).
>>>>
>>>> I've been bench-testing it the last few days with a wimpy power supply.
>>>> Surprisingly, I'm up to 500 wattts out with 1300 volts on the plates.
>>>>
>>>> I have several tubes, and have tried a couple of different pairs. In
>>>> both instances I've noticed that one tube will have a slightly brighter
>>>> plate glow than the other.
>>>>
>>>> I'd like to have the tubes as closely matched as possible.
>>>>
>>>> My question is: Which tube is most likely to be the better, the bright
>>>> one, or the cooler one?
>>>>
>>>> 73,
>>>> Barrie, W7ALW, DN36au,
>>>> QRV 6M, 432&  1296 EME
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps at contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>