Re: Bayou Jumper Adapterless Spotting [2 Attachments]


David Martin <davemrtn@...>
 

If you are tuning around 'real' slow looking for it, you'll never find it.

Tune toward where you think it should be, just as if you are trying to change the freq. by a couple of MHz.

You'll need the ATTEN @ max, REGEN up pretty high and the volume up near half.

As you are turning the Tuning Knob you'll hear a little pop and you'll think "what the heck was that".  That is what you are looking for.  Once you find it, you can do "small", but not slow, tuning adjustments till you are satisfied you got the 'bump'.

NA1MH


On 1/12/2017 14:44, RWeeks neotoxo54@... [4sqrp] wrote:
 
This all very interesting reading....
BUT, what is this bump you talk of...
AND, what is the proper procedure for tuning the receiver to the crystal freq. by essentially shorting the crystal across the antenna connection.

I think I understand and I made a little rig to do just this thing but this "Bump" escapes me.



SENT FROM MY IPAD MINI
Rocky Weeks, AF5AF
East Arkansas Fur Takers, FTA Chap 29B
Arkansas Trappers Assoc.
South Western Arkansas Fur Takers, FTA Chap 29A

On Jan 12, 2017, at 13:17, Bry Carling af4k@... [4sqrp] <4sqrp@...> wrote:

 

This is cool. It's more or less the same technique used in the old days for lapping trays of crystals to frequency. The machine would have two terminals connected to the antenna of an Eddystone HF receiver and you could hear the whole group of crystals 'singing.' Maybe 48 at one time! Fun stuff... (that was done by me at Cathodeon Crystals in England, 1971.)

Best regards - Brian Carling
AF4K
117 Sterling Pine St.
Sanford, FL 32773

Tel: 321-262-5471




On Jan 12, 2017, at 1:48 PM, Jim Sheldon w0eb@... [4sqrp] <4sqrp@...> wrote:

 
Thanks Chip, but Dave Martin thought this one up, I just implemented it.  This forum has been a clearinghouse for ideas on making the Bayou Jumper work better and better.

Jim

On Jan 12, 2017, at 12:41 PM, CStratton groups@... [4sqrp] <4sqrp@...> wrote:

Brilliant work Jim!

It all keeps getting simpler and simpler, but not too simple!

Chip
AE5KA

On Thu, Jan 12, 2017 at 9:40 AM, 'Jim Sheldon' w0eb@... [4sqrp] <4sqrp@...> wrote:
 

After a couple of cups of coffee, I finished the little elevated copper strap ground near the antenna connector.  This allows you to touch one pin of the crystal to the center conductor of the BNC connector and the other to the elevated ground (placed far enough away that it won't interfere with connecting the antenna but close enough to reach with one crystal pin.  Works like a champ.  If you do something like this, you won't even need to carry an adapter around with you.  It doesn't even look terribly out of place on the face of the Bayou Jumper.  Your mileage may vary.


By the way, the crystal spotting technique being touted here actually works on superhet receivers as well.  Not quite as pronounced a "Thump" but the indication is there.  I tried it on my K3S and it was very close to the crystal's actual frequency.  Whoever it was that said he didn't think this was repeatable for all builds, sorry to inform you, but if you have your receiver operating properly, it will work.  The real SOE spies using the original Para set radios did it this way (they had regen receivers that overloaded easily too).  The idea of using the Bayou Jumper's internal receiver just isn't feasable.  The output of the oscillator is too strong and there is too much stray coupling internally that can't be eliminated to allow the regen receiver to operate without overload, period.  Reducing the output of the oscillator is not possible either as it quits working before any significant reduction in output can be achieved.  The design guys would have to come up with a whole new PC board with shield cans around just about everything.  The inductors etched into the PC board would have to be removed and replaced with toroids and a whole bunch of other things to isolate the oscillator from the receiver (even with the antenna input grounded) to reduce the level to the point it could be heard in the RX without overload.  I'm sure N5IB and others on the design team (I'm not one of them) will chime in on this as well.

Jim - W0EB






--
David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------

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