|
Title: two stages or three? Post by: N0BST on May 13, 2006, 07:29:46 PM I was thinking of building a sortof PW class AM transmitter with an old CVM-0 mod transformer I acquired. It'll be about 20W with an 807 output. For the RF chain I was wondering if it would be best to use a buffer to drive the 807 or if there is enough isolation to just drive the 807 directly with the oscillator? I'm wanting to avoid any incidental FM-ing or phase modulation.
As they say in Brooklyn when the Fifth Armored Division rolls through, Tanks, Scott Todd Title: Re: two stages or three? Post by: Bacon, WA3WDR on May 14, 2006, 02:09:42 PM I would put a buffer in - a tetrode or pentode.
Title: Re: two stages or three? Post by: WD8BIL on May 15, 2006, 03:17:18 PM No doubt... Bacon is right... put a buffer stage in there.
It'll help the stability of the osc. Title: Re: two stages or three? Post by: W1FRM on May 20, 2006, 08:08:12 AM I agree ......... use a buffer. The rig shown in my avatar ("Baby T.") uses
a single 807 final at either 10 or 20 watts (variable plate voltage). A driver stage is almost mandatory for most VFO's. I used a 6V6 and it also is a doubler on 80 and 40 meters. Take care in shielding the stages from the VFO and each other to avoid pulling and "wobulation" (FM'ing). Good Luck! Title: Re: two stages or three? Post by: K1JJ on May 20, 2006, 12:25:05 PM Yes, a buffer is needed unless you desire the SBE effect. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
For a circuit that is DESIGNED to wobulate somewhat, check out my VXO xtal controlled power oscillator PW rig . It would wobble much more if it didn't use a xtal. This rig was designed to be as simple as possible. 5W out, fully self contained. Still used today. http://www.amwindow.org/tech/htm/series.htm Guy - is that Baby-T in your avatar? If so, I didn't know it had a digital readout. Neat looking rig, OM. T |