From: Patrick Jankowiak (recycler@swbell.net)
Date: Sun Apr 09 2006 - 20:27:22 PDT
The final in that radio (and the RT246) is rated for 100W dissipation. On
1:1 - zero
If the radio is putting out 35 watts, the tube is likely burning up 35
If your radio has been "hot rodded" and is putting out 50 or 60 watts, then
The tube used in there, in reality a conduction-cooled UHF triode, is very
After all of this, though, I would add that if transmissions are kept very
Some people have drilled a weep hole in the bottom of the adjustable
Some experts on the list may correct me on these matters.
PJ
Chance Wolf wrote:
> ----- Original Message -----
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.
1.5:1 - 4%
2:1 - 11%
3:1 - 25%
4:1 -I don't remember but it's worse.
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.
the SWR best be kept below 2:1
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.
short, the thing can run into any load.
section of the antenna to allow it to drain. Don't know how well that works.
> 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!)
>
>
>
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