[Boatanchors] more on the Johnson Johnson

[Bill Cromwell]

Hi,

I'm Sure some list members might choke or something reading about a DDS 
driving a boat anchor. I know there are others who have done the same 
thing you are doing :) If you go through the Johnson VFO and get the 
keying all pointed up it will be pretty clean. The VFO is grid-block 
keyed and sequenced so that any shift in frequency when the key is 
pressed will settle before the signal gets through to the finals and on 
the air. It also switches off slightly after the finals stages turn off 
when you release the key. Some of those VFOs are pretty clean. The one 
in my Heathkit DX-100 sounds pretty good, too.

Having said all of that, I am working up a heterodyne VFO inspired by 
the Hallicrafters HA-5. The VFO (~5 MHZ) and a crystal oscillator run 
all the time without being switched (keyed). The benefit is no chirps, 
yoops, or whoops with keying AND better temperature stability (once 
warmed up). The mixer and any output matching circuits are keyed while 
the oscillators are isolated from keying and keying load changes. Your 
idea of shifting to the alternate VFO during receive to move it out of 
the receive passband is an old idea that works well. Certainly the DDS 
systems will accommodate that. You can have memory frequencies too :)

The Hallicrafters HA-5 is on the BAMA site and you can see more details 
of what I am working on. To handle some of the WARC bands the VFO would 
have to shift a different range to avoid spurious output. A DDS would 
better accommodate that :)

73,

Bill  KU8H


On 10/23/2018 03:26 PM, Brian wrote:
>
> BA purists should stop reading now.... not so very offensive words below. Namely DDS...
> Thanks to those who replied to my query about the CW note of my recent Ranger acquisition.
>
> I did do a monitoring on a receiver that was some amount physically separated from the xmtr and the CW does not quite have the sound I got in a receiver in the room with the Johnson itself. I appreciate that there is a vintage sound to the CW and that cognoscenti will pick up on it as something not of today per se. Not all that objectionable.
>
> I believe from peering thru the vent holes on top that the rig does have the desired keyer mod...so I might be going into that and seeing if adjusting R39 does any positive affect. And tighten any screws and bolts etc against VFO leakage and whatnot.
>
> Following on the fact that the crystal I tested it out with (versus the internal VFO) had a somewhat more bell like tone.... I went a bit further.
> I have a DDS based VFO that is a counter and VFO built as one unit....so.... having previously used it on a rig that has no VFO at all ....
> I put it on the Ranger and get a quite nice CW note out of it. So it is the EFJ VFO that contributes I think mostly to the vintage CW sound and not the xmtr...PA etc. so much. I think.
> What is nice about the DDS VFO is that it has a SPLIT mode...so that I can run it (and not hear it on the receiver) at a frequency up from where I an listening and then use the Split VFO B on a keyline to actuate the B VFO when I xmit (there is a rcvr MUTE and an external  amp activate keyline on the T/R switch I have),
> Not purist at all, but is a nice add of technology for those out there who might shy away from the vintage CW note on a CQ or answer to a CQ. We will see as the winter season progresses. And it is a solution I can apply to other small EFJ xmtrs lacking a VFO I  would like to get on the air as well as a Heath DX 40 (and maybe bigger iron like an EFJ Viking II etc. if I ever come across them again at all and can add them to the cold basement winter solution.... HI).
>
>
> tnx
> Brien VE3VAW Toronto
>
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-- 
bark less - wag more