From: Patrick Jankowiak (recycler@swbell.net)
Date: Tue Apr 11 2006 - 17:27:20 PDT
Is it the thermal runaway issue with Ge or the current carrying capacity? I
was thinking somewhere I read they were rated 15A but could be mistaken.
PJ
Buzz wrote:
> The problem with running high power on the 524/246 is the heavy load on the DC
> to DC power supply, especially the early radios with germanium power
> transistors.
>
> Buzz
>
>
>
> On Sun, 09 Apr 2006 22:27:22 -0500, you wrote:
>
>>The final in that radio (and the RT246) is rated for 100W dissipation. On
>>low power, it can run indefinitely into any load. The radio is supposed to
>>run at 35W on High power. If the PA is tuned correctly (as set by someone
>>who knows how to work on those radios), it can handle poor antenna matches
>>very well. As a reference, the SWR roughly indicates how much of the
>>forward power is reflected (as reverse power) back from the antenna to the
>>final amplifier, and is therein dissipated as heat in the tube.
>>
>>1:1 - zero
>>1.5:1 - 4%
>>2:1 - 11%
>>3:1 - 25%
>>4:1 -I don't remember but it's worse.
>>
>>If the radio is putting out 35 watts, the tube is likely burning up 35
>>watts as heat to do that. (the total power into the tube is 70 watts) If
>>you have a 3:1 SWR, then 25% of that 35W gets reflected back into the tube,
>>adding 8.75 watts to the heat. Now the tube dissipates 43.75 watts. Almost
>>half of what it is rated for. -So it's not as bad as it looks but for 4:1 I
>>would leave it on low power.
>>
>>If your radio has been "hot rodded" and is putting out 50 or 60 watts, then
>>the SWR best be kept below 2:1
>>
>>The tube used in there, in reality a conduction-cooled UHF triode, is very
>>efficient at the low frequencies the radio is used at, the voltage on the
>>tube is lower (only 650V I think) than it can take, and the things are
>>really bulletproof. I think it's the CC version of the 2C39.
>>
>>After all of this, though, I would add that if transmissions are kept very
>>short, the thing can run into any load.
>>
>>Some people have drilled a weep hole in the bottom of the adjustable
>>section of the antenna to allow it to drain. Don't know how well that works.
>>
>>Some experts on the list may correct me on these matters.
>>
>>PJ
>>
>>
>>Chance Wolf wrote:
>>
>>
>>>----- Original Message -----
>>>From: "Patrick Jankowiak" <recycler@swbell.net>
>>>To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
>>>Sent: Saturday, April 08, 2006 5:17 PM
>>>Subject: Re: [MV] NOS military radio antenna base MX-2799 AB-719/VRC on Ebay
>>>
>>>
>>>
>>>
>>>>Kobs? We don't need no steenking knobs!
>>>>
>>>>Yeah there's no knob, but the SWR plot is <2 from 30 to 90 MHz.
>>>
>>>
>>>Yeah. As compared to the MX-6707 which seems to always be 2+ even on Happy
>>>Days. Supposedly the RT-524 can handle a continuous SWR of 4, but given the
>>>price of finals I don't think I'd care to put it to the test!
>>>
>>>I was actually going to leave a meter permanently hooked up in the line so I
>>>could always tell when my MX-6707 decided to become a swimming pool, but
>>>never got around to it. I've had lots broil. At least now I give the knob
>>>a spin before doing anything with the radio, and make sure the servo cycles
>>>with a flick of the RT-524's band switch. I guess I should be keeping a
>>>cover on the 6707s when not in use, but I never remember to do stuff like
>>>that when it counts.
>>>
>>>(I had both mine fail in quick succession when I was on the way to San Jose
>>>for the convention the one year, so I was out of comms for most of the trip.
>>>Really annoying!)
>>>
>>>
>>>
>>>===Mil-Veh is a member-supported mailing list===
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>>>
>>
>>===Mil-Veh is a member-supported mailing list===
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>
>
> =Mil-Veh is a member-supported mailing list===
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> To reach a human, contact <ackyle@gmail.com>
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>
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