[AMRadio] AMRadio Digest, Vol 73, Issue 11


Rob Atkinson ranchorobbo at gmail.com
Fri Feb 12 18:52:26 EST 2010


thanks Pete and Bernie i'll do that.  i have a HT20 that uses that tube.

Rob
K5UJ

On Fri, Feb 12, 2010 at 5:38 PM, Bernie Doran
<qedconsultants at embarqmail.com> wrote:
> 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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