|[AMRadio] TS430 as VFO on a KNIGHT T60|
John Coleman ARS WA5BXO
wa5bxo2006 at pctechref.com
Sun Oct 15 15:44:08 EDT 2006
Yes, by all means give it a whirl. That's how discoveries are made.
Funny, that you should mention the SB200 in that way. BJ, WB5PKD, and I are
using the SB200 to drive the grids of the 250THs. We drive the SB200 with a
modified TS820. The TS 820 put about 10 watts into the SB200 and the SB200
puts about 60 watts into the push pull grids of the 250Ths. We have checked
the SB200 out as an AM linear and found it to be equivalent to a pair of
6146s plate modulated, like a DX100 or Apache but with better audio using
the TS830 or the modified TS820. We modified the TS820 so that with the
flip of a switch it would bypass the SSB filter and allow carrier injection
while in the LSB mode position. This makes it a great AM rig for about
15-20 watts carrier. As you found out the plates on the finals of the SB200
or red but they are a little red at idle current with no carrier. We tried
to put extra bias on the SB200 to bring the plate current to cut off and a
little past cutoff. Then applying more drive to get the carrier out that we
wanted but with a little more efficiency. It helped some but then required
more drive from the TS820 causing it to heat up a little more. I guess
there is no substitute for bigger tubes. HIHI so we just run it a little
lower and limit the Xmit time.
As for control carrier, I would rather run SSB.
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of KA5MIR
Sent: Sunday, October 15, 2006 1:35 PM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] TS430 as VFO on a KNIGHT T60
Controlled carrier has tradeoffs. You are trading reduced linearity and
tricker audio adjustment for greater PEP. Not that it can't be done and
sound reasonably good.
Another point is that tubes with zirconium or titanium on the plate NEED
get red to getter properly. I'd be more concerned about the power supply
than the red plates. But that's just SSB amps in general. I don't have any
experience with the SB200.
It would probably be easier and more productive to just reduce the carrier
power on the 430 until you're happy with the amp. I doubt anyone on the
other end would notice 20 or 50 watts difference and your audio would
probably sound cleaner too.
But the main thing is to have fun and enjoy your radios. If you want to
put the T60 on the air, by all means drive it with a little carrier from the
430 until you get your crystals. You won't have to worry about being on
On Sunday 15 October 2006 11:42, Jack Schmidling wrote:
> My thoughts on an advantage of the T60 is that, as it has
> controlled/suppressed carrier, the idle power is a lot less than the
> TS430. As a consequence, I could drive a linear (SB200) a bit harder
> and get more power out of it than when using the 430.
> When running the 430 at about 15 watts, and a plate current of 150 ma on
> the amp, the plates get redder than I like. Seems like I should be able
> to increase the input significantly with the T60 before the plates got
> to the same temp.
> Is this correct reasoning?
> I think I will just get some xtals for the T60 as I am getting a Ranger
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