Topics

Ozark Patrol Tuning adjustment question


Curt
 

Can anyone advise about adjusting the Ozark Patrol tuning range?  On the top band, mine covers 4.6-16.2 MHz, a range of 11.6.  The marked dial is 5-12 or a range of 7.
On the bottom band it covers 3.3 - 4.5 range of 1.2, marked range 3-5 range of 2  So the range is small on the lower band but wide on the upper band.

The radio functions fine as it stands, but would like to get it set closer to the dial.  I am wondering if adjusting the pad/trim trimmers on the variable capacitor would provide some improvement? 

Suggestions?

Curt KB5JO


Jerome Wysocki
 

Hi Curt,

The most likely thing to do, I think, is to replace (change the value) of c11, a 560 pF capacitor, that is wired to the toggle switch, that is your band switch. I believe with the 560 pF capacitor switched in the circuit, to parallel it to c1 (the 365 pF variable tuning capacitor) you are on the higher frequency band, and when c11 is not in parallel with c1, you are tuning the lower frequency band. (I hope my logic isn't reversed here.)

I also found that increasing the battery voltage from 9 to 15 volts, the tuning ranges changed noticeably on both bands. That might be another option to experiment with. (15 volts also gives much higher audio to the speaker.)

How is your regeneration control doing? Mine was very unstable on both bands until I inserted a 10 ohm resistor in series with the one turn (feedback) loop that goes to the center of the torroid coil ring. (I've built a number of regenerative receivers before, so am familiar with good ones and unstable ones.) I connected the resistor to the one turn loop, on the side that was outside the center of the torroid coil. That vastly improved the stability of the regeneration control. Encouraged by this, I will fine tune the resistor value to see if I can get even smoother regeneration. (Greater that 10 ohms, and I lose all regeneration, but I might get better stability with, say 8 ohms. I will have to try this.)

How does the performance on the two bands of your receiver compare? Mine is now very stable and useable for cw and ssb on 80 meters, but no luck yet on the top band, for 40 meters.

Hope this helps you out.

... Jerry Wysocki, KC9JXE


Curt
 

My regeneration works well on both bands.  I listen to 80 & 75 in the evening, 40, 30, and 20 during the day.  I added a little tiny LM386 audio amplifier so now can listen to everything without headphones. 

My only issue, which isn't a large one is that my tuning cant match up the the index marks on the dial. 

Curt KB5JO


Curt
 

Here is what it sounds like on 40M:


Jerome Wysocki
 

Thanks, Curt. Your audio files sound just like my receiver does on 80 and 75 meters, but only after the addition of the 10 ohm resistor to the one turn feedback coil going through the center of the torroid coil, as I described it. Mine does not like long antennas, so I use a 30 foot longwire. Furthermore, I substituted a small adjustable trimmer capacitor to replace the gimmick capacitor in the original design. This allows me to better control the input from possible overload by reducing the coupling with the antenna. Adjusting that trimmer helped me do precisely that.

I tried substituting a 2N2222 for the original detector transistor, but found nothing really significantly different in receiver performance with either one. All resistors were within spec when I tested them, prior to installation. Maybe some critical capacitors surrounding the detector transistor are marginal, relative to their specs, and are just off enough to cause the problem I am having. (I carefully observed that no mistakes were made in part identifications, prior to soldering them into place.) No solder bridges or cold joints were observed either, as far as I can see. Voltages appear normal.

Thanks again, Curt. I'm sure I'm missing something simple, and I'll probably kick myself when I find it 🙂. Meanwhile, it works really well on cw and ssb on 80 and 75 meters, and is good enough for a QRP cw receiver on that band.

... Jerry Wysocki, KC9JXE


Timothy East
 

I was very happy to see the mods for the Murania kit to really improve its performance.
Is there a list of mods that I can use to improve my OZark Patrol?

Tim
K0EMP

On Apr 21, 2020, at 19:00, Jerome Wysocki <jeromewysocki48@...> wrote:

Thanks, Curt. Your audio files sound just like my receiver does on 80 and 75 meters, but only after the addition of the 10 ohm resistor to the one turn feedback coil going through the center of the torroid coil, as I described it. Mine does not like long antennas, so I use a 30 foot longwire. Furthermore, I substituted a small adjustable trimmer capacitor to replace the gimmick capacitor in the original design. This allows me to better control the input from possible overload by reducing the coupling with the antenna. Adjusting that trimmer helped me do precisely that.

I tried substituting a 2N2222 for the original detector transistor, but found nothing really significantly different in receiver performance with either one. All resistors were within spec when I tested them, prior to installation. Maybe some critical capacitors surrounding the detector transistor are marginal, relative to their specs, and are just off enough to cause the problem I am having. (I carefully observed that no mistakes were made in part identifications, prior to soldering them into place.) No solder bridges or cold joints were observed either, as far as I can see. Voltages appear normal.

Thanks again, Curt. I'm sure I'm missing something simple, and I'll probably kick myself when I find it 🙂. Meanwhile, it works really well on cw and ssb on 80 and 75 meters, and is good enough for a QRP cw receiver on that band.

... Jerry Wysocki, KC9JXE



Curt
 

"I believe with the 560 pF capacitor switched in the circuit, to parallel it to c1 (the 365 pF variable tuning capacitor) you are on the higher frequency band, and when c11 is not in parallel with c1, you are tuning the lower frequency band. (I hope my logic isn't reversed here.)"

To clarify, with the 560 pF switched into the circuit, the resonant frequency of the circuit with the 1.6 uH tank, will be about 3.7 MHz.  With it switched out, the frequency will be about 7 MHz.  I listen to the oscillator in another receiver to find where the Ozark is tuned.

I have read that the Paraset regenerative receivers used by resistance in WW2 put out strong signals from their oscillators that Gestapo used to locate the clandestine radios.  The operators had to limit their time listening to decrease possibility of being detected ( and executed ).

Curt KB5JO


Gwen Patton
 

Perhaps our British members might be able to verify if this is how the BBC's roving radio detection vans would locate people who hadn't paid their radio license fees? I've seen pictures of these vans, with DF loops on them, to sniff out scofflaws, and I wonder if that's what they were designed to detect.

73,
Gwen, NG3P

On Wed, Apr 22, 2020 at 10:43 AM Curt via groups.io <rhulett1=consolidated.net@groups.io> wrote:
"I believe with the 560 pF capacitor switched in the circuit, to parallel it to c1 (the 365 pF variable tuning capacitor) you are on the higher frequency band, and when c11 is not in parallel with c1, you are tuning the lower frequency band. (I hope my logic isn't reversed here.)"

To clarify, with the 560 pF switched into the circuit, the resonant frequency of the circuit with the 1.6 uH tank, will be about 3.7 MHz.  With it switched out, the frequency will be about 7 MHz.  I listen to the oscillator in another receiver to find where the Ozark is tuned.

I have read that the Paraset regenerative receivers used by resistance in WW2 put out strong signals from their oscillators that Gestapo used to locate the clandestine radios.  The operators had to limit their time listening to decrease possibility of being detected ( and executed ).

Curt KB5JO



--

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Jenny Everywhere's Infinite: Quark Time
http://quarktime.net


w9ran
 

On 4/22/2020 11:32 AM, Gwen Patton wrote:
Perhaps our British members might be able to verify if this is how the BBC's roving radio detection vans would locate people who hadn't paid their radio license fees? I've seen pictures of these vans, with DF loops on them, to sniff out scofflaws, and I wonder if that's what they were designed to detect.
Not since 1971: https://www.sixtiescity.net/Television/Licences.htm

I suspect by then there were few if any regens still in use,  but while radio licenses were required those vans did try to DF the weak radiation from local oscillators in superhet receivers in an attempt to find unlicensed receivers.   Had to be unrewarding work ;-)

73, Bob W9RAN


Frank Perkins
 

No Gwen,
Those British vans are searching for tea &  crumpet shops!    :-)
Frank N6CES

On Wed, Apr 22, 2020, 9:32 AM Gwen Patton <ardrhi@...> wrote:
Perhaps our British members might be able to verify if this is how the BBC's roving radio detection vans would locate people who hadn't paid their radio license fees? I've seen pictures of these vans, with DF loops on them, to sniff out scofflaws, and I wonder if that's what they were designed to detect.

73,
Gwen, NG3P

On Wed, Apr 22, 2020 at 10:43 AM Curt via groups.io <rhulett1=consolidated.net@groups.io> wrote:
"I believe with the 560 pF capacitor switched in the circuit, to parallel it to c1 (the 365 pF variable tuning capacitor) you are on the higher frequency band, and when c11 is not in parallel with c1, you are tuning the lower frequency band. (I hope my logic isn't reversed here.)"

To clarify, with the 560 pF switched into the circuit, the resonant frequency of the circuit with the 1.6 uH tank, will be about 3.7 MHz.  With it switched out, the frequency will be about 7 MHz.  I listen to the oscillator in another receiver to find where the Ozark is tuned.

I have read that the Paraset regenerative receivers used by resistance in WW2 put out strong signals from their oscillators that Gestapo used to locate the clandestine radios.  The operators had to limit their time listening to decrease possibility of being detected ( and executed ).

Curt KB5JO



--

-+-+-+-+-
Jenny Everywhere's Infinite: Quark Time
http://quarktime.net


Tom Denton
 

When I asked this question of Russ Ramirez, this was his reply: 


On Sun, Mar 24, 2019, 5:11 PM Russ Ramirez <russ.ramirez@...> wrote:
Typically to get a dial on a receiver, signal generator, etc. you have an adjustable coil for the low-end of the band in question and a variable cap for the high end. In this case, the inductance is fixed and yes, the 560 pf capacitor can probably be increased a little to bring things in line. A 680 pf cap may not be excessive, but if it is, then another cap in parallel will be additive. If you happen to have a small trimmer cap to solder in parallel, that would be a good way to dial things in.

 


Curt
 

So the British actually charged people a fee to LISTEN to a radio??!!  Wonder how their DF vans would have dealt with a crystal set.  Maybe if caught with a 1N34A or Oatmeal box wound with wire in the house the bobbies would put the cuffs on :-o

Curt KB5JO


Jerome Wysocki
 

I heard the same story about radiation from the regenerative Paraset receivers, and how they could be tracked down with direction finding radio receivers. So I fired up one of my experimental regenerative radios, but only used about 32 volts for the detector B+. It regenerated fine so I took a small portable hand held short wave radio with me for a walk around the neighborhood. With the set in my house still oscillating, I could pick up its radiated signal for at least several hundred feet away from my house. Imagine the range I could have gotten if I increased to detector B+ up to around 250 volts or so, typically to what a regenerative Paraset radio would be operating with. No wonder they were careful to minimize listening time!


W6BOW
 

Jerome,

Fascinatin' stuff. Thank you for sharing.

Don    W6BOW


-----Original Message-----
From: Jerome Wysocki <jeromewysocki48@...>
To: main@4SQRP.groups.io
Sent: Wed, Apr 22, 2020 11:37 am
Subject: Re: [4SQRP] Ozark Patrol Tuning adjustment question

I heard the same story about radiation from the regenerative Paraset receivers, and how they could be tracked down with direction finding radio receivers. So I fired up one of my experimental regenerative radios, but only used about 32 volts for the detector B+. It regenerated fine so I took a small portable hand held short wave radio with me for a walk around the neighborhood. With the set in my house still oscillating, I could pick up its radiated signal for at least several hundred feet away from my house. Imagine the range I could have gotten if I increased to detector B+ up to around 250 volts or so, typically to what a regenerative Paraset radio would be operating with. No wonder they were careful to minimize listening time!



John Nicholas
 

War time Restrictions.    Owning and listening was not the real issue.  It was owning and listening to Nazi broadcasts as a cover for spying.   Finding an unlicensed  receiver, might uncover a transmitter used for spying.

John Nicholas
KE0ZUW

On Apr 22, 2020, at 12:39 PM, Curt via groups.io <rhulett1@...> wrote:

So the British actually charged people a fee to LISTEN to a radio??!!  Wonder how their DF vans would have dealt with a crystal set.  Maybe if caught with a 1N34A or Oatmeal box wound with wire in the house the bobbies would put the cuffs on :-o


Lee Bahr
 

The Paraset was only issued to agents in rural locations because of the regenerative signal.  Even then it was dangerous to be using one.

Lee, w0vt

On 4/22/2020 9:43 AM, Curt via groups.io wrote:
"I believe with the 560 pF capacitor switched in the circuit, to parallel it to c1 (the 365 pF variable tuning capacitor) you are on the higher frequency band, and when c11 is not in parallel with c1, you are tuning the lower frequency band. (I hope my logic isn't reversed here.)"

To clarify, with the 560 pF switched into the circuit, the resonant frequency of the circuit with the 1.6 uH tank, will be about 3.7 MHz.  With it switched out, the frequency will be about 7 MHz.  I listen to the oscillator in another receiver to find where the Ozark is tuned.

I have read that the Paraset regenerative receivers used by resistance in WW2 put out strong signals from their oscillators that Gestapo used to locate the clandestine radios.  The operators had to limit their time listening to decrease possibility of being detected ( and executed ).

Curt KB5JO


W5ESE
 

They still do; although now it's assessed on television sets. It originally was assessed on radio receivers.

https://www.theguardian.com/media/2019/dec/16/qa-how-the-bbc-is-funded-by-tv-licences

They're considering abolishing it; as some feel the BBC has become increasingly biased.


Tom Sevart
 

On 4/22/2020 16:25, W5ESE wrote:
They still do; although now it's assessed on television sets. It originally was assessed on radio receivers.
https://www.theguardian.com/media/2019/dec/16/qa-how-the-bbc-is-funded-by-tv-licences
They're considering abolishing it; as some feel the BBC has become increasingly biased.
When I was over there serving with the USAF, in the summer of 1993 we had the last Friendship Fete that I attended on our base since I left at the end of that summer. They had a TV detector van on display and a guy showed me how the equipment worked. Basically they had a spectrum analyzer display inside the van and really not much else. There were antennas installed on each corner of the roof of the van, which IIRC consisted of a small horizontal dipole in front of a reflecting screen.

--
Tom Sevart N2UHC
St. Paul, KS

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Tom Denton
 

Back to the original question. When I asked Russ Ramirez this same question he replied:

Typically to get a dial on a receiver, signal generator, etc. you have an adjustable coil for the low-end of the band in question and a variable cap for the high end. In this case, the inductance is fixed and yes, the 560 pf capacitor can probably be increased a little to bring things in line. A 680 pf cap may not be excessive, but if it is, then another cap in parallel will be additive. If you happen to have a small trimmer cap to solder in parallel, that would be a good way to dial things in.

I posted this earlier but cutoff Russ' reply.

Tom 
w9kkq


Curt
 

Ok, since the 560 pF cap isn't in the circuit for the 5-12 MHz scale, assumes this means need to add some capacitance in parallel with the capacitor to bring the top frequency down.  QSL the trimmer, but I thought that was what the trimmers on the back of the variable capacitor were for, to adjust the tracking of the tuning.  Adjusting these makes no difference for me. 

For the 1.6 uH tank, the maximum frequency now is about 15.5 MHz which implies a capacitance of 70pF.  At 12 MHz implied capacitance is 110pF.  So, I assume putting a 40 pF cap in parallel with the tank will get the tuning to track the dial markings?  I think I have a 50 pF trimmer and will give that a try.

Thanks,

Curt KB5JO