[AMRadio] AM Usage with Linear AMPS

Brian Carling bcarling at cfl.rr.com
Tue Nov 23 07:25:29 EST 2004

I thought that the WRL DuaoBander mobile was only SSB.

On 22 Nov 2004 at 22:11, John Coleman, ARS WA5BXO wrote:

> My experience (which is very little when it come to these sweep tube
> rigs) is they or rated for a belch or some thing short and don't hold up
> to a fix channel field day adventure with out tube replacement.  I had a
> DuaoBander mobile for a while rated a 400 watts PEP input I never saw
> more than 150 watts output while whistling in the mike.  It was in
> perfect condition and would light a 50 watt bulb with normal speech.  I
> thought it would have blown it out.  I was very disappointed. Yet, it
> was one of the most heard radios all over the country by many AMers in
> the late 80s.
> John, WA5BXO
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Brian Carling
> Sent: Monday, November 22, 2004 9:55 PM
> To: Discussion of AM Radio
> Subject: RE: [AMRadio] AM Usage with Linear AMPS
> Aren't there a lot of commercially built amateur radio linear 
> amplifiers and RF finals that exceeded he manufacturers MAX 
> Pdiss rathings over the years, by adding a COOLING FAN to take 
> away the extra heat?
> One thinks of MANY sweep tubes rated for so-called Pdiss of 16 
> watts and 20 watts that are regularly run at hundreds of watts of 
> RF! The tubes don't seem to melt.
> I think of the ubiquitous 6JS6C with a rating of 30 watts.
> Yaesu ran a pair of these at 260 watts input in their FT101 series.
> Many guys ran them at 260 watts p.e.p. on SSB and 260 watts CW.
> Assuming 65% efficiency, you have 35% of 260 watts going into 
> the plates. That is to say 91 watts split between the two tubes.
> UH oh - POP! But no, they didn't.
> Then when you throttle that FT-101 back to 40 watts input on AM
> and go to your 30% efficiency (if it is) then you are actually 
> putting only 20 watts carrier per tube which is SAFER.
> Is that correct?
> How about some of the othre rigs that rated their 2 sweep tube 
> finals for 560 Watts or even 800 watts!?
> Then youhave peak Pdisses of 140 to 200 watts between the two 
> sweep tubes, most of which are rated for no more than 40 watts.
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