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

Fri Sep 17 04:26:33 EDT 2010

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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