[ARC5] TRF, Direct Conversion, Regens and Superhets.

Leslie Smith vk2bcu at operamail.com
Fri Sep 17 04:39:11 EDT 2010


Jeez, Les, you do go on at times .....


> ----- Original Message -----
> From: "Leslie Smith" <vk2bcu at operamail.com>
> To: "Discussion of AN/ARC-5 military radio equipment." <arc5 at mailman.qth.net>
> Subject: [ARC5] TRF, Direct Conversion, Regens and Superhets.
> Date: Fri, 17 Sep 2010 09:26:33 +0100
> 
> 
> Hello list,
> If I was asked to list the characteristics used to identify the 
> various kinds of receivers - superhets, TRF and Regenerative 
> Receivers and DC receivers I would place some emphasis on which 
> stages provide gain.
> 
> In a crystal set, clearly a TRF receiver, there is no amplifying 
> device.  The power delivered to the earpiece is provided by the 
> antenna.
> 
> In a Direct Conversion receiver, ALL the gain (as much as 100dB) 
> comes in AF stages, after the detector.  However, putting a high 
> gain AC coupled amplifier does not turn a crystal set into a DC 
> set.  You can't receive SSB or CW on a crystal set.  The function 
> of the detector is involved in the definition.
> 
> In a TRF receiver, there is a division of gain between the RF and 
> AF stages.  Somewhere between 30 to 60 dB in each section; the RF 
> gain is made at the frequency of the transmitted signal.  ALL of 
> the RF gain.
> 
> (I don't know why I'm writing this ...  There is no point.  
> Every-one know this ...)
> 
> A regenerative detector circuit can be used in both a superhet or a 
> TRF receiver.  It is a method of detection, not a type of receiver. 
>   In the first case the set may be called a super-gainer or "Jones" 
> superhet.  Frank C Jones did a great deal to popularise the 
> regenerative superhet.  We all know the benefits of regeneration, 
> (perhaps 30dB or gain and improved selectivity) so I won't take up 
> that topic.  Regeneration is a process that can't be used to define 
> a type of receiver - it's an adjective applied to a noun.
> 
> In a conventional "super" the gain circuits operate at the 
> frequency of the transmitted signal (which may vary) and at a fixed 
> intermediate frequency.  (How am I doin' fellas?  What have I left 
> out ...  What about "supers" with a tuneable IF? Collins? Drake?  
> Barlow-Wadley?)  OK I'll remove the word "fixed" and replace it 
> with "non-transmitted" frequency.  The detector operates at a 
> non-transmitted frequency.   I think that defines a superhet.   
> Finally, we have gain after the detector (say 25 to 40dB) at audio 
> frequencies.
> 
> Dare I press the send button?  Ok, ok, I got carried away with an 
> interesting question - what characteristics define a specific class 
> of receiving set?  I guess I didn't cover everything, but basically 
> my answer depends on the frequency where gain is "got", and the 
> operating frequency of the detector.  I'll finish before I cop a 
> bucket of cold water.
> 
> Now, to get on topic - AN/ARC-5 sets.  All the ARC-5 "command" 
> receivers are superhets.  None are DC receivers.  RAK and RAL are 
> TRF receivers.   Having got on topic, (forgive me for being brief) 
> I'll end before the eggs arrive.  *splattt
> 
> 
> Les
> 
> 
> 
> 
> > ----- Original Message -----
> > From: "Henry Mei'l's" <meils at get2net.dk>
> > To: "Bob Macklin" <macklinbob at msn.com>, "Discussion of AN/ARC-5 
> > military radio equipment." <arc5 at mailman.qth.net>
> > Subject: Re: [ARC5] Regeneration, and the RU, among others.
> > Date: Fri, 17 Sep 2010 09:08:42 +0200
> >
> >
> > Maybe I remember wrong, but I thought a DC receiver was made up of a
> > combination of a TRF receiver (no IF circuits) where detection takes place
> > by hetrodyning/beating a locally generated  signal against the received (non
> > frequency-converted) HF signal, whereas a
> > "straight, classic" TRF receiver signal uses some kind of
> > detection/rectifiaction device to extract/seperate the the audio from the
> > (often amplified)
> > received RF signal. I suppose whether or not a
> > regenerative/super-regenerative receiver is a special form of TRF receiver
> > is a moot point.
> > According to the 1979 ARRL Handbook.pp 8-7, 8-8: "Direct-Conversion
> > Recievers ...direct-conversion or synchrodyne type ... the detection stage
> > of this receiver is actually a product detector that operates at the desired
> > signal frequency."
> > (I thought I "invented" the DC receiver when I was a teenager -- but found
> > out that I wasn't first on the idea ;0)
> >
> > Henry, Cph.  OZ1UF/exK2UOC/etc.
> >
> >
> >
> > ----- Original Message -----
> > From: "Bob Macklin" <macklinbob at msn.com>
> > To: "Discussion of AN/ARC-5 military radio equipment."
> > <arc5 at mailman.qth.net>
> > Sent: Friday, September 17, 2010 2:30 AM
> > Subject: Re: [ARC5] Regeneration, and the RU, among others.
> >
> >
> > BFO on or off, since there is no conversion to an IF it is a direct
> > conversion Rx.
> >
> > Bob Macklin
> > K5MYJ
> > Seattle, Wa.
> > "Real Radios Glow In The Dark"
> > ----- Original Message -----
> > From: "Kludge" <wh7hg.hi at gmail.com>
> > To: "'Discussion of AN/ARC-5 military radio equipment.'"
> > <arc5 at mailman.qth.net>
> > Sent: Thursday, September 16, 2010 5:02 PM
> > Subject: Re: [ARC5] Regeneration, and the RU, among others.
> >
> >
> > -----Original Message-----
> > From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
> > Behalf Of Kenneth G. Gordon
> > > I have used several U.S. military TRF receivers, mostly those for
> > > VLF, but my favorite, the RAL for HF. There is absolutely
> > > NOTHING requiring "two-handed" operation. Even the regen
> > > control has an auxiliary pot attached to the rear of the main tuning
> > > dial that automatically compensates for the change in regen
> > > setting across a band.
> >
> > That pot on the tuning mechanism would be the "second hand".
> >
> > > Also, there was an article in a recent issue of ER concerning the
> > > RU, which is also a TRF. The author found it to be a really
> > > excellent receiver. It, also, does NOT require "two handed"
> > > operation.
> >
> > Okay, let's make this simple.  (I know some of the symbology is off; it's
> > been a while.)
> >
> > TRF != regenerative detector.  TRF = TRF.  Regen = regen.  Regen = some form
> > of adjustment of regen control across tuning range - a "2nd hand", meat or
> > mechanical.
> >
> > RAL = regen = mechanical 2nd hand with provisions for meat.
> >
> > RU = TRF.  RU != regen.  !Regen = !regen control = !"second hand."
> >
> > Also, RU = built-in BFO that tunes with the Rx.
> >
> > And finally, for reference purposes, homemade (or just home) regen sets !=
> > military equipment.
> >
> > > His conclusion was that the RU was, essentially, a really superb
> > > Direct Conversion receiver.
> >
> > Odd.  The BFO is only on when in CW.  Did he actually check out the
> > schematic or find a manual and follow the circuit description?  In AM, the
> > BFO is off which means it suddenly isn't DC but a just plain old grid
> > detector doing what grid detectors do, that being detect.  While the end
> > result in CW & SSB may functionally emulate a DC receiver, it is by no means
> > one at all.  That's kind of like saying a command Rx has a product detector
> > since it acts like it does when the BFO is on.
> >
> > Best regards,
> >
> > Michael, WH7HG BL01xh
> > http://www.nationalmssociety.org/chapters/NTH/index.aspx
> > http://wh7hg.blogspot.com/
> > http://kludges-other-blog.blogspot.com
> > Hiki Nô!
> >
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