[AMRadio] AMRadio Digest, Vol 73, Issue 11


Bernie Doran qedconsultants at embarqmail.com
Fri Feb 12 18:38:38 EST 2010


Fair radio in Lima, Ohio had a huge stock of them, I believe thousands at a 
very reasonable price, give them a call or email. Bernie W8RPW
----- Original Message ----- 
From: "Rob Atkinson" <ranchorobbo at gmail.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Friday, February 12, 2010 1:55 PM
Subject: Re: [AMRadio] AMRadio Digest, Vol 73, Issue 11


Jim, where do you get a 4D32 these days?

thanx

rob
K5UJ

>
> Jack,
>
> First off, I have an HT-20 on the air and it does well on AM, so the 
> problem is not generic to the transmitter design. I have not used a light 
> bulb for a dummy antenna, at least not recently, but my average-reading 
> watt meter does not bobble during modulation. I would expect a light bulb 
> to get brighter during modulation, not dimmer, which is something you also 
> know.
>
> From the list of things that Larry suggested, above, I would not think 
> that #1 would not be a cause of this particular problem. Human voice audio 
> is not symmetric, so you can achieve more full modulation by selecting the 
> better phasing connection, but neither phasing connection should cause 
> "downward modulation." #5 is also not likely to be the problem if the rig 
> has the original modulation transformer. The other suggestions are all 
> likely causes. Another one might be a very flat (low gain, low emission) 
> 4D32 final amplifier tube.
>
> Let me know how much final grid drive you are running and what the loaded 
> plate current is for the final amp. The manual recommends 260 ma plate 
> current for CW and 320 ma for phone, but I don't run any more than 200 ma 
> for either phone or CW. 4D32's are too expensive! It also recommends 10 ma 
> for grid current. The ARRL Handbook ratings for a 4D32 are a maximum of 
> 240 ma for CW and 220 ma for phone, with 12 ma of grid current for the CW 
> condition and 10 ma for phone. I can compare your operating parameters to 
> the ones I'm running currently on my rig. Mine is tuned up on 14286 right 
> now in anticipation of the Classic Exchange AM event on Sunday.
>
> Good luck,
>
> Jim Hanlon, W8KGI
> ______________________________________________________________
>
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