[HBR] Regen Birdies

[Ron Barlow via HBR]

Hi Bill,
 My 24A/27/27 regen does not have an RF stage. Many of the "old time" regen circuits, that I have seen, used untuned RF stages, and thus would have shared this particular "birdie" response issue.
 I don't remember for certain (that happens a lot these days!), but I may have had the regen control advanced beyond the most sensitive position (at the very threshold of oscillation), at the time that I observed this phenomena. I suspect that this would increase the magnitude of this "birdie" response, due to an increase of harmonic energy output, from the oscillating detector.
 Anyway, I just wanted to pass along what I believed to be a rather interesting and perhaps unusual problem.
                           73 de Ron n4gjv  
--------------------------------------------
On Mon, 1/12/15, Bill Cromwell <wrcromwell at gmail.com> wrote:

 Hi Ron,
 
 Did that regen have an rf amp
 and the associated tuned circuits? A regen 
 doesn't need an rf amp for signal gain as
 the detector has plenty. An rf 
 amp isolates
 the detector from the antenna and helps with rejection of
 
 signal 'far' removed from the
 operating frequency. My regens have the rf 
 amp and the tuning is tracked with the
 oscillating detector. There is a 
 gain
 control on the rf amp that really acts more as a variable
 
 attenuator. Some fellows add a
 potetntiometer in series with the antenna 
 to reduce the input signals but that does
 nothing to filter signals 
 outside the band
 of interest.
 
 73,
 
 Bill  KU8H
 
 
 On 01/12/2015 08:43 PM, Ron
 Barlow via HBR wrote:
 > Hi Bill,
 >   I recently learned that, at
 least under extraordinary conditions, regens actually can
 have birdie problems. I was using a hb regen, while
 listening to 160m. I was hearing legit 160m signals well
 enough, but I was puzzled by the fact that I was also
 hearing numerous CW signals below 1800 Khz.
 >   I discovered that the 2nd
 harmonic of the oscillating regen detector, was beating
 against incoming 80m signals, to yield audio output.
 >   This problem was greatly
 exacerbated by the fact that I was using an 80m dipole, as a
 receive antenna.
 >   As a
 result, the ~ 3.5 Mhz signals, that were delivered to the
 receiver, were actually much stronger than the desired ~
 1.75 Mhz signals.
 >   I made
 certain to use the 160m antenna, for receive, as well as
 xmit purposes, after that experience!
 > 
                                73
 de Ron  n4gjv