[HBR] HBR-8 Questions

[Helmut Usbeck]

>Howdy folks;
>
>This is my first post to the HBR list. I've been a ham for 30=
 years
>now and
>I'm finally getting around to homebrewing some receivers. I'd=
 like
>to start
>with the simple HBR-8 but was wondering if it would be possible=
 to
>just add
>an AM detector without the other changes via the HBR-11. I'd=
 like to
>also
>use the receiver to listen to AM SW broadcasts in the 40 mtr=
 band.
>Please
>forgive this next stupid question but I noticed there is a BFO
>switch on the
>HBR-8 yet the article mentions "treating the AM signal exactly=
 as
>though it
>were SSB".
>
>I guess what I'm asking is, why is there a BFO switch if=
 carrier
>injection
>is always required to receive CW and SSB with the product=
 detector?
>Doesn't
>turning off the BFO disable you from receiving SSB and CW? I=
 would
>think
>just shutting off the BFO would allow you to receive AM. (with=
 a
>diode
>detector?)
>
>
>Thanks for the help gang! I'm looking forward to some building=
 fun
>in the
>future!
>
>
>
>Glenn K2KL

There's no reason why you can't include a diode detector for AM 
detection.  The HBR-11 doesn't have an AM detector either  You=
 should 
be able to receive SW stations with the 40 meter coils.  Coils=
 for 
other SW bands can be wound.  To receive AM with a product=
 detector 
one must zero beat the station.  This sometimes referred to as 
exalted carried detection of AM signals.  I prefer using some=
 type of 
an AM detector though.  If one turns off the BFO on a well=
 designed 
product detector you shouldn't hear much of the AM signal.  The 
product detector tube is really a mixer, not a rectifier.  A=
 study of 
the receiver section in the ARRL handbook would clarify this for=
 you.
-- 
Helmut Usbeck, WB2ADT vze2gmp4@verizon.net on 04/24/2002