[HBR] Tracking

[Bill Cromwell]

Hi Brian,

In your superhet the *real* tracking is between the VFO and the 
"rest-of-the-front-end". The inductors and capacitors in the 
rest-of-the-front-end will all be on the same frequncy and could/should 
be about identical. So even of the frequency change 'bunches up' at one 
end they should all 'bunch up' the same. The VFO is on a different 
frequency and THAT is where the 'tracking' issues really arise. I have 
used radios that use the tuning knob for only the VFO and separate 
"peaking" knob that tunes the rest-of-the-front-end. Those will also 
accommodate tuning in the image and on some receivers gives coverage of 
WWV when the radio otherwise does not tune anywhere near WWV. Those tune 
the image "backward".

Instead of two or three more controls you have one more control. Image 
tuning might be considered a *feature*. Tracking the stages in the 
rest-of-the-front-end might still be required during alignment but is a 
much more trival exercise than tracking the VFO with the 
rest-of-the-front-end. Tuning the rest-of-the-front-end and VFO 
separately will relieve you of needing that three section variable cap. 
The rest-of-the-front-end will use a dual section cap with two identical 
sections and they might be different from the single section VFO cap.

I recommend staying as close to the design as possible if you hope to 
benefit from any of the troubleshooting info available. When things 
don't work as expected you will have to wonder if it's your own 
modifications or another error that might be covered in the existing 
books, web pages, mail lists, and CDs you might have.

Build the next one with the rest-of-the-front-end separate from the VFO 
and with everything else the same. Etc. Make changes one step at a time.

I have started using the amber plastic pill bottles for coil forms.  My 
XYL gets them in various sizes. She needs a lot of medication to stay 
alive so I have bought her a personal snow shovel for handling all her 
meds in trade for the empty bottles.

73,

Bill  KU8H


On 11/28/2014 04:53 PM, Brian Burns wrote:
> Hello Walt,
>
> "....but if you don't have the front end peaked to perfection the receiver
> goes dead, so the Q is certainly high enough."
>
> Please keep in mind that I don't know squat about building an HBR, and am
> just trying to learn about the process.
>
> >From reading the various materials that I've collected there seems to be
> quite a bit of time and energy spent fiddling with each band's set of coils
> to get a three bay variable capacitor to track properly, especially over a
> wide band.
>
> Has anyone tried doing an end run around the tracking problem by having
> separate capacitors for RF, LO, and Mixer, and putting up with a lot of knob
> twisting in exchange?
>
> Cheers,
>
> Brian
>
>