Re: [AMRadio] Home brew AM Cathode modualtion
I appreciate all of the suggestions. I'm not locked into a particular tube configuration yet, but I have to admit there is something appealing about running the 450TH. It's probably my mental image of two of them lit up behind a glass window in the front panel :) Clay W7CE - Original Message - From: John Coleman, ARS WA5BXO [EMAIL PROTECTED] To: 'Discussion of AM Radio' amradio@mailman.qth.net Sent: Sunday, October 03, 2004 12:37 PM Subject: RE: [AMRadio] Home brew AM Cathode modualtion The Rice neutralization circuit works better with a higher Q grid tank and, if possible, some input swamping or grid load resistor. The biggest trouble with the circuit is that the loading of the grid tank is not constant over the full RF cycle as a result the Q and balance is shifted somewhat over the period of the RF cycle. Starting with a higher Q or C value is one way of minimizing this effect. The circuit does work because I used it as well and also with a 304TLs, back in the days of experimenting with the ultra modulation or balanced high level modulation circuits. I eventually went to standard Push Pull. John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Sunday, October 03, 2004 12:45 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Home brew AM Cathode modualtion The 450th is a big triode, so I don't think you can run it single ended pie net output, you would need to do 2 250th tubes in push pull or something, but the 450th would do the cathode modulator quite well. You could use a single-ended pi-network type output circuit, with a balanced grid tank coil. That is knows as Rice neutralisation. You don't get as perfect null as you can with a balanced plate tank cincuit or a pushpull arrangement, but it works well enough that it became the standard design of tube type broadcast transmitters starting in the late 50's. I used that circuit with the first high power rf final I ever built, using a 304-TL in the final, because I didn't have a large split stator tuning capacitor on hand. Don K4KYV __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
[AMRadio] Collins Collectors Association First Wednesday AM Night Oct. 6th!
FIRST WEDNESDAY AM NIGHT !!! Sponsored by the Collins Collectors Association. Cedar Rapids, Iowa - Wednesday Oct. 6th on 3880 kcs at 7:30PM local East Coast time marks the start of the latest chapter of First Wednesday AM Night, drawing hundreds of vintage stations from across the country. The event is anchored by a tall ship AM station in each time zone. The East Coast will run for 90 minutes in response to the tremendous participation in the Eastern Time zone. The remaining time zones will be an hour. We encourage stations to check-in on AM using Collins and other transmitters, new and old. It's an opportunity to revel in this nostalgic mode, enjoy giving vintage equipment a run, and sharing some storytelling about classic vacuum tube homebrew and commercial designs. Typically more than a hundred stations take part in the evening's coast-to-coast AM event; by the time it concludes at 10P, PDT (1A EDT). A logbook of check-ins, with the equipment used, appears in the Announcements Events section of www.amfone.net on the page's AM Forum - BBS. In months past, anchor stations have included those running the beautiful Collins 300-G, pictured below, as well as those running the amateur KW-1, and other noted models. http://www.amwindow.org/pix/jpg/300g.jpg LISTEN for the following anchors and stop by to say hello, won't you? You don't have to be running Collins or vintage gear to be welcomed into the group. 7:30P-9P East Coast Anchor: Bob W0YVA in Great Falls VA 8P-9P Central Anchor: Jim W0NKL Ft. Scott KS 8P-9P Rocky Mountain Anchor: Jim WA0LSB in Larkspur CO 8P-9P West Coast Anchor: Bill N6PY in Palmdale CA comments please to [EMAIL PROTECTED]
Re: [AMRadio] BTA-250 and 1-K schematic
It's there. My website is unfortunately very popular and I have but an ADSL line at 384K, so sometimes if someone's sucking down a huge document, things can time out for others. I wish I had a hardware fix to equalize all visitor's bandwidths. http://208.190.133.201/bta250/schem.html Patrick, When I go to this site I dont get anything. Is it still there? thanks Don
RE: [AMRadio] BTA-250 and 1-K schematic
It does suggest: NOTE: some web browsers don't want to display a picture this size. Might be best to download it. so, right click and save as or save target as, etc.. then use a viewer. I could do a PDF I suppose. but it's a half meg file, so please allow a few seconds to save. Patrick
