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" <[email protected]> To: "Discussion of AM Radio in the Amateur Service" <[email protected]> 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 > ______________________________________________________________ > ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
