[Boatanchors] Dx40 and VF1

[RAY FRIESS]

Many of the older transmitters were of similar simple design when it came to those used by we Novices, which makes me wonder if they had the same type of problem as the DX 40 when it came to using them with a VFO.    For instance, would we find similar concerns with the Hallicrafter HT 40, or the Knight T 60?  They both use an external VFO which can be powered by the transmitter itself.


________________________________
From: Hal Dale <wb4aeg at zoho.com>
Sent: Wednesday, November 7, 2018 10:31 AM
To: RAY FRIESS
Cc: boatanchors; Boatanchors QTH; Glen Zook
Subject: Re: [Boatanchors] Dx40 and VF1

Guy's few of the early(Novice) transmitters had adequate power supplies. Heath was also guilty up and until the DX60.. Developing multi voltages from a single winding using high wattage dropping resistors is and was not efficient...But, it was cheap....I guess at the time, this at the novice level was acceptable...Hal/WB4AEG


---- On Wed, 07 Nov 2018 11:55:10 -0500 RAY FRIESS <rayfrijr at msn.com> wrote ----

Is the HG 10 vfo less of a load on the DX 40 than the VF1?

________________________________
From: Glen Zook <gzook at yahoo.com<mailto:gzook at yahoo.com>>
Sent: Wednesday, November 7, 2018 7:57 AM
To: RAY FRIESS; boatanchors; Boatanchors QTH
Subject: Re: [Boatanchors] Dx40 and VF1

The VF-1 was actually designed to be used with the AT-1 transmitter. Then, they came out with the DX-35 which had a transformer that failed on a regular basis without any additional load on the transformer and only a relatively small percentage of DX-35 transmitters still have an original working transmitter.



Then, Heath came out with the DX-40. That transmitter had a slightly better transformer than the DX-35. Unfortunately, the transformer still failed on a regular basis but not quite as many as in the DX-35. It was not until the DX-60 series that the transmitter had a really reliable transformer.



The added load from powering the VF-1 from either the DX-35 or DX-40 is often just enough to cause a transformer that is just on the edge of failure to fail. Running the VF-1 from a separate regulated power supply also helps prevent "chirping" because of varying voltage.



The VF-1 can be greatly improved in both stability and tendency to chirp by replacing the 6AU6 with a 6AH6 and replacing the 0A2 screen regulator with an 0B2. Neither tube replacement requires and modification to the VF-1. Then, use the 0A2, removed from the VF-1, to regulate an external power supply that provides 150 VDC regulated to the VF-1. This lower plate voltage works fine.



On CW, let the VF-1 run constantly when transmitting and chirp just doesn't happen. Of course, you have to put the VF-1 in standby when receiving. This can be accomplished with a set of relay contacts that are connected to a phone plug plugged into the back of the VF-1.



Glen, K9STH

Website: http://k9sth.net


________________________________
From: RAY FRIESS <rayfrijr at msn.com<mailto:rayfrijr at msn.com>>
To: boatanchors <boatanchors at mailman.qth.net<mailto:boatanchors at mailman.qth.net>>; Boatanchors QTH <boatanchors at qth.net<mailto:boatanchors at qth.net>>
Sent: Wednesday, November 7, 2018 12:08 AM
Subject: [Boatanchors] Dx40 and VF1

I'm a bit puzzled by something. I keep reading things about the problems or dangers of powering a VF1 from the DX 40 instead of using a separate power supply. What puzzles me is would Heath engineers really have built the vfo to be powered by the 40 if it was going to be a problem? Or would they really have put a power supply into the 40 that was so underrated and overtaxed that it couldn't handle a VFO???

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