[HBR] HBR-??

[hbr@mailman.qth.net]

In a message dated 1/27/04 7:45:47 AM Eastern Standard Time, 
Bill@LizCurtisHiggs.com writes:


> The reason for trying the 6JH8 is that I have some.

Good reason. I've had trouble with RF feedthrough in a single-ended 7360 
mixer, which is why the Type 7 has an RF stage.

 After reading Pat Hawker's note in Amateur Radio Techniques about the 6JH8 
as 
> a replacement for the 7360, and finding some on sale at $2 each, I bought 3 
> to play with. I'll allow some room around the first mixer area so if I want 
> to try one later, I can.
> 
> 700kc tuning range: the original idea was to stick with the 1600kc IF of the 
> HBR-16, so I had obtained a 1515kc crystal for the second conversion 
> oscillator (2nd IF is 85kc). With a 1600kc IF you need to tune 5050 to 5750 to cover 
> all of 80 and 40 in an imaging design allowing for a 50kc overage on each 
> end. This offsets the bands more than the 1700kc IF of the classical band 
> imaging design.

Works. Plus it gives a bit of flexibility when you do the upper bands via 
converter - you don't need exactly the right xtal.


> 
> As my usual oscillator design is to calculate L/C values based on range 
> desired, measured min/max on the cap - then try what "looks right" and diddle 
> with it until I get what I want. I may try a series cap: as I have three 
> sections to play with (plus the internal trimmers), I do have several options.

Note that the osc trimmers in that cap are in series...


> 
> Next weekend: power supply. The transformer I was planning to use is only 
> rated for 70ma, which may be too low, especially if I draw additional current 
> in the front end. I have another transformer salvaged from a Motorola 2-way 
> which will give me 275v at somewhat more current. Problem is, it's bigger, so 
> I'll have to check the fit (BEFORE drilling holes).
> 
> 

External power supply! Move the heat and hum and weight out of the rx 
chassis.


73 de Jim, N2EY


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