Topics

Tuning problems


AllanIsaacs
 

I've experienced tuning problems with valve radios over the years and I wonder if modern test equipment might shed some light on at least one cause.
Recently I aligned an IF amplifier which worked fine on small signals but gave odd results on strong signals (the Murphy 62B).
Tuning across an AM broadcast on a shortwave band gave a nice tuning peak on the S-Meter on all three available bandwidth settings but tuning across Radio 4 on 198KHz gave completely different tuning points on these three bandwidths.
No doubt the IF signal was very much greater on Radio 4. One possibility is the AGC action was affecting the tuning of the IF transformers by changing the valve characteristics?
I noted that as a test signal at the IF was increased the response of the IF strip changed from a decent single peak to several peaks. The implication is as one tunes across a strong signal the S Meter will either indicate more than one peak or integrate the results to show a large peak at the wrong frequency.
For example I see a peak for Radio 4 ranging from 192KHz at 8KHz, to 198KHz at 1KHz bandwidth.
Has anyone noticed this effect?
Allan G3PIY


Michael O'Beirne
 

Allan

 

I’m wondering if the strange tuning of the IF amp is the result of the Miller Effect. (I had to look it up in an old RSGB Handbook).  The increasing AGC voltage with a stronger signal is effectively changing the capacitance of the IFT and lowering the resonant frequency. 

 

In the manual for the BRT400 it says:

 

               “A portion of the cathode resistor of the second [IF] amplifier is unbypassed, this applies negative feedback, reducing the detuning which might occur when a strong signal is being received.”

 

However, if you leave part of the cathode unbypassed that will reduce the IF gain and may upset the AGC performance. 

 

I have read that neutralising the amplifier is also a way to reduce the Effect.  

 

I’m sure others here will have better ideas.

 

73s

Michael

G8MOB

 

From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of AllanIsaacs
Sent: 11 November 2020 11:03
To: wireless-set-no19@groups.io
Subject: [wireless-set-no19] Tuning problems

 

I've experienced tuning problems with valve radios over the years and I wonder if modern test equipment might shed some light on at least one cause.
Recently I aligned an IF amplifier which worked fine on small signals but gave odd results on strong signals (the Murphy 62B).
Tuning across an AM broadcast on a shortwave band gave a nice tuning peak on the S-Meter on all three available bandwidth settings but tuning across Radio 4 on 198KHz gave completely different tuning points on these three bandwidths.
No doubt the IF signal was very much greater on Radio 4. One possibility is the AGC action was affecting the tuning of the IF transformers by changing the valve characteristics?
I noted that as a test signal at the IF was increased the response of the IF strip changed from a decent single peak to several peaks. The implication is as one tunes across a strong signal the S Meter will either indicate more than one peak or integrate the results to show a large peak at the wrong frequency.
For example I see a peak for Radio 4 ranging from 192KHz at 8KHz, to 198KHz at 1KHz bandwidth.
Has anyone noticed this effect?
Allan G3PIY

_._,_._,_

 


AllanIsaacs
 

That sounds like the perfect explanation for what I’ve found Michael.

I had the idea to set the receiver up with a spectrum analyser set on say 200KHz with a scan of say 100KHz then disconnect the AGC line and feed it from a variable bias supply to see if the response curve changes in shape. Ideally the height should diminish as negative bias increases but if the shape changes then that would prove the action of the Miller effect, if that’s what it is. It might be an EF91 grid or anode capacitance changing as its anode voltage changes (like a varicap) and if the IFTs are very sensitive to capacitance change that would explain things. The IF is 500KHz and the tuning discrepancy for Radio 4 is about 6KHz which shows up as a distance of an inch on the B40 dial. Unless what I describe below can partly explain things!

 

I think I’ve discovered the reason for the difficulty in tuning 40m SSB on the B40.

I exposed the 4-gang tuning condenser (hidden under a shield) and found it was essentially hanging in mid-air. As the spindle is turned, the first thing to happen is the whole frame rotates before the vanes move. Reversing the direction, the frame rotates back again, before the vanes move the other way. The overall effect is a huge backlash in tuning. Certainly, I can see one loose mounting screw and probably all three are loose. The frame is basically being held in place by flexible grounding braids and the connections to the four sections. A clue was a faint knocking noise as direction of tuning was reversed.

Allan G3PIY


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of Michael O'Beirne via groups.io
Sent: 11 November 2020 14:14
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Allan

 

I’m wondering if the strange tuning of the IF amp is the result of the Miller Effect. (I had to look it up in an old RSGB Handbook).  The increasing AGC voltage with a stronger signal is effectively changing the capacitance of the IFT and lowering the resonant frequency. 

 

In the manual for the BRT400 it says:

 

               “A portion of the cathode resistor of the second [IF] amplifier is unbypassed, this applies negative feedback, reducing the detuning which might occur when a strong signal is being received.”

 

However, if you leave part of the cathode unbypassed that will reduce the IF gain and may upset the AGC performance. 

 

I have read that neutralising the amplifier is also a way to reduce the Effect.  

 

I’m sure others here will have better ideas.

 

73s

Michael

G8MOB

 


Michael O'Beirne
 

Allan

 

The Miller effect has been known since the 20’s and I have no doubt that competent receiver designers would factor that in.  I don’t recall ever having found that problem with my other old HF radios.

 

That loose ganged capacitor is more likely to be the cause.  I have never encountered a loose tuning capacitor.  Perhaps no one has checked that capacitor for years, especially hidden under the shield.    May be on board a warship the constant vibration loosened the nuts, but in operational service the B40 would have had a detailed servicing every six months or so. These sets were out of service by the mid-1960s so who knows what has happened since?

 

Let’s see what happens when you have tightened up the nuts and maybe clean up and re-lube the wipers at the same time. 

 

73s

Michael

G8MOB 

 

From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of AllanIsaacs
Sent: 11 November 2020 16:04
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

That sounds like the perfect explanation for what I’ve found Michael.

I had the idea to set the receiver up with a spectrum analyser set on say 200KHz with a scan of say 100KHz then disconnect the AGC line and feed it from a variable bias supply to see if the response curve changes in shape. Ideally the height should diminish as negative bias increases but if the shape changes then that would prove the action of the Miller effect, if that’s what it is. It might be an EF91 grid or anode capacitance changing as its anode voltage changes (like a varicap) and if the IFTs are very sensitive to capacitance change that would explain things. The IF is 500KHz and the tuning discrepancy for Radio 4 is about 6KHz which shows up as a distance of an inch on the B40 dial. Unless what I describe below can partly explain things!

 

I think I’ve discovered the reason for the difficulty in tuning 40m SSB on the B40.

I exposed the 4-gang tuning condenser (hidden under a shield) and found it was essentially hanging in mid-air. As the spindle is turned, the first thing to happen is the whole frame rotates before the vanes move. Reversing the direction, the frame rotates back again, before the vanes move the other way. The overall effect is a huge backlash in tuning. Certainly, I can see one loose mounting screw and probably all three are loose. The frame is basically being held in place by flexible grounding braids and the connections to the four sections. A clue was a faint knocking noise as direction of tuning was reversed.

Allan G3PIY


 


Pete_G4GJL
 

The B40 Tuning cap is actually an Achilles Heel in the radio. It has 4 sections and is fairly heavy, being made of slightly heavier frame metal than the 19-set or 1154 types.
Furthermore it has a 1/2 inch ceramic shaft.
 
To avoid the likely shattering during heavy gunfire, the designers used a flexible shaft coupler and crucially brass sheet springy supports to bear the main weight of the cap. If I recall correctly, these are soldered, each  being made in two parts. The brass ages with temperature (recently mentioned on the VMARS reflector) and mechanically ages due to the flexure effect of tuning. Out of  the 70 or so sets I have worked on, easily 20% had this failure and had to be partially dismantled to effect a repair.
 
Alan, do check, before you reassemble the cap and its covers etc,  that the signal wires on the underside of the cap have not snapped or fatigued due to the excessive moving around of the variable cap.
 
The grub screws holding the shaft coupler to the shaft are cushioned  by a single lead shot between the grub screw and the ceramic shaft.
 
Pete
G4GJL

On Wed, Nov 11, 2020 at 5:23 PM Michael O'Beirne via groups.io <michaelob666=ntlworld.com@groups.io> wrote:

Allan

 

The Miller effect has been known since the 20’s and I have no doubt that competent receiver designers would factor that in.  I don’t recall ever having found that problem with my other old HF radios.

 

That loose ganged capacitor is more likely to be the cause.  I have never encountered a loose tuning capacitor.  Perhaps no one has checked that capacitor for years, especially hidden under the shield.    May be on board a warship the constant vibration loosened the nuts, but in operational service the B40 would have had a detailed servicing every six months or so. These sets were out of service by the mid-1960s so who knows what has happened since?

 

Let’s see what happens when you have tightened up the nuts and maybe clean up and re-lube the wipers at the same time. 

 

73s

Michael

G8MOB 

 


AllanIsaacs
 

I’ve taken some pictures Pete but not too easy to do this.

The rear has what looks like a phosphor bronze strip (held in place by a bracket) to which a single screw secures it to a bush mounted on the frame.

The front is a bit odd. There’s a steel plate screwed to the frame by two screws and below this another steel plate secured to the chassis but nothing connecting these two plates. The only connection to the front of the tuning condenser is the flexible coupler.

The rear screw is very loose.

All the wires are intact.

I should be able to access the rear screw, but is there something missing at the front, it seems strange to have two metal plates doing nothing? Maybe they’re just a sort of buffer to prevent the condenser moving too far front to back?

 

Also the label has extra letters “EMD/R”. Any idea what these mean? It clearly is an AP677571.

http://www.radiomuseum.co.uk/Murphy62brepair.html

Allan G3PIY


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of Pete_G4GJL
Sent: 11 November 2020 17:35
To: wireless-set-no19@groups.io Notification
Subject: Re: [wireless-set-no19] Tuning problems

 

The B40 Tuning cap is actually an Achilles Heel in the radio. It has 4 sections and is fairly heavy, being made of slightly heavier frame metal than the 19-set or 1154 types.

Furthermore it has a 1/2 inch ceramic shaft.

 

To avoid the likely shattering during heavy gunfire, the designers used a flexible shaft coupler and crucially brass sheet springy supports to bear the main weight of the cap. If I recall correctly, these are soldered, each  being made in two parts. The brass ages with temperature (recently mentioned on the VMARS reflector) and mechanically ages due to the flexure effect of tuning. Out of  the 70 or so sets I have worked on, easily 20% had this failure and had to be partially dismantled to effect a repair.

 

Alan, do check, before you reassemble the cap and its covers etc,  that the signal wires on the underside of the cap have not snapped or fatigued due to the excessive moving around of the variable cap.

 

The grub screws holding the shaft coupler to the shaft are cushioned  by a single lead shot between the grub screw and the ceramic shaft.

 

Pete

G4GJL

 

 


Andy_G8JAC
 

 

>>Also the label has extra letters “EMD/R”. Any idea what these mean?

 

 

I was hoping for a response from a Navy Tech who knows, but as a bit of logical speculation:  Electronic Maintenance Devonport? 

EMR is also often seen which following this logic could be R= HM Dockyard Rosyth, and also EMP which could be HM Dockyard Portsmouth.?

The /R almost certainly indicates Refurbished [by].  The original manufacturers code is usually barred out.

 

The PF suffix on your tag probably indicates original manufacture in June 1958.

 

Andy  G8JAC


AllanIsaacs
 

Michael

I received an excerpt from the G2DAF receiver write up re the Miller effect which I’ll add to my repair notes.

No doubt lots of experimenters have puzzled over the effect especially as test equipment reveals more detail.

Allan G3PIY


AllanIsaacs
 

That sounds about right Andy.

Makes the receiver more interesting. I wonder if they forgot to tighten the tuning condenser screw or maybe it jus unscrewed by itself?

You can see where the guy started to punch the first letter then must have decided to try again in the right place.

Perhaps it got a brand new set of valves at Devonport. I think I collected it from someone near Salisbury so a Southern dockyard is quite feasible if it was auctioned off later?

Allan G3PIY

 

 

>>Also the label has extra letters “EMD/R”. Any idea what these mean?

 

 

I was hoping for a response from a Navy Tech who knows, but as a bit of logical speculation:  Electronic Maintenance Devonport? 

EMR is also often seen which following this logic could be R= HM Dockyard Rosyth, and also EMP which could be HM Dockyard Portsmouth.?

The /R almost certainly indicates Refurbished [by].  The original manufacturers code is usually barred out.

 

The PF suffix on your tag probably indicates original manufacture in June 1958.

 

Andy  G8JAC

 


Michael O'Beirne
 

Allan

 

The key document for the original G2DAF receiver is the extended pamphlet put out by the RSGB in the early-mid 1960s encompassing the original articles in the Bulletin.  I have a copy but can’t lay my hands on it ATM.  I can only access the 1968 Handbook.  I think Thorley went into design details on dealing with AGC and the Miller effect.  I noticed that the RF amp in the original design (an ECC84 cascode) is neutralised.  Not sure if that was to tame the amp or to deal with the Miller effect.  The improved FE using a 6BZ6 for the RF amp has an un-bypassed cathode resistor providing negative feeedback, but bypassed at the bottom end for the RF Gain pot in series.

 

However, given the evidence from G4GIL of the non-rigid fixing of the ganged FE capacitors, I think that aspect calls for your prime investigation.  I’ll check on this when I get round to my B41.

 

Since your 62B is now unlikely to have to endure the blast of naval guns, I’d be inclined to remove the “suspension” and bolt the capacitors rigidly to the chassis.  You may need spacers to maintain the same height. 

 

73s

Michael

G8MOB

 

 

From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of AllanIsaacs
Sent: 13 November 2020 08:50
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Michael

I received an excerpt from the G2DAF receiver write up re the Miller effect which I’ll add to my repair notes.

No doubt lots of experimenters have puzzled over the effect especially as test equipment reveals more detail.

Allan G3PIY

_._,_._,_

 


AllanIsaacs
 

Hi Michael

The G2DAF booklet is in hand thanks.

I copied the Miller page from G4GJL to my report and I’ve decided not to modify the 62B and keep it original (except for the new mains connector).

The IF amp and RF amp have full decoupling which means there’s none of the negative feedback solution suggested by G2DAF incorporated.

As long as I use the RF gain and AGC switch appropriately all should be well.

The tuning condenser needed only its mounting screw (there’s only one!) tightening and that aspect is dealt with. There’s even a special hole in the metalwork for access to this.

Not entirely convinced about the guns though as on certain days tanks from the Dorset ranges near here can make our windows rattle, although the Naval exercises tend to be shooting in the other direction. Those tanks are so noisy there are even road signs warning motorists not to worry unduly.

 

I’ve just done the final IF alignment with a spot of twiddling left to do on the wavebands.

Next, I’ll be designing my new active aerial. I’ve ordered a suitable weatherproof plastic box and I spotted half a dozen large ferrite rods complete with coils so bought those. The new varicaps arrived the other week. With a bit of luck this (mounted on a pole away from buildings) should do away with most of the racket messing up the bands. I had an idea to use one ferrite rod for L/M/S and another wound with a large coil for VLF.

I wonder if anyone’s tried this sort of antenna?

Allan G3PIY


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of Michael O'Beirne via groups.io
Sent: 13 November 2020 13:51
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Allan

 

The key document for the original G2DAF receiver is the extended pamphlet put out by the RSGB in the early-mid 1960s encompassing the original articles in the Bulletin.  I have a copy but can’t lay my hands on it ATM.  I can only access the 1968 Handbook.  I think Thorley went into design details on dealing with AGC and the Miller effect.  I noticed that the RF amp in the original design (an ECC84 cascode) is neutralised.  Not sure if that was to tame the amp or to deal with the Miller effect.  The improved FE using a 6BZ6 for the RF amp has an un-bypassed cathode resistor providing negative feeedback, but bypassed at the bottom end for the RF Gain pot in series.

 

However, given the evidence from G4GIL of the non-rigid fixing of the ganged FE capacitors, I think that aspect calls for your prime investigation.  I’ll check on this when I get round to my B41.

 

Since your 62B is now unlikely to have to endure the blast of naval guns, I’d be inclined to remove the “suspension” and bolt the capacitors rigidly to the chassis.  You may need spacers to maintain the same height. 

 

73s

Michael

G8MOB

 


Mike
 

In the day job before retirement, we did a lot of design work for the MoD, including organising all the various trials.  Interestingly, the worst spec for vibration was for tracked vehicles.  (With the possible exception of submarines being depth charged)  The tracked vehicle specs were really severe and quite a lot of kit came back from initial trials in kit form.  Then of course we had to do EMP tests, and I don't mean from lightning…  There was a test facility at Farnborough but that's gone now I believe.  I bet the local Amateurs hated that when it 'fired'!  Amazing place.

 

73, Mike,

Mike Stevens,

G8CUL/M0CUL/F4VRB.

 

From: wireless-set-no19@groups.io On Behalf Of AllanIsaacs
Sent: 13 November 2020 14:36
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Hi Michael

The G2DAF booklet is in hand thanks.

I copied the Miller page from G4GJL to my report and I’ve decided not to modify the 62B and keep it original (except for the new mains connector).

The IF amp and RF amp have full decoupling which means there’s none of the negative feedback solution suggested by G2DAF incorporated.

As long as I use the RF gain and AGC switch appropriately all should be well.

The tuning condenser needed only its mounting screw (there’s only one!) tightening and that aspect is dealt with. There’s even a special hole in the metalwork for access to this.

Not entirely convinced about the guns though as on certain days tanks from the Dorset ranges near here can make our windows rattle, although the Naval exercises tend to be shooting in the other direction. Those tanks are so noisy there are even road signs warning motorists not to worry unduly.

 

I’ve just done the final IF alignment with a spot of twiddling left to do on the wavebands.

Next, I’ll be designing my new active aerial. I’ve ordered a suitable weatherproof plastic box and I spotted half a dozen large ferrite rods complete with coils so bought those. The new varicaps arrived the other week. With a bit of luck this (mounted on a pole away from buildings) should do away with most of the racket messing up the bands. I had an idea to use one ferrite rod for L/M/S and another wound with a large coil for VLF.

I wonder if anyone’s tried this sort of antenna?

Allan G3PIY


 


AllanIsaacs
 

Maybe you got involved with HDRS Mike, maybe not but one of our containers rolled on the M6 and MoD insisted on an independent full trial somewhere in the SE.

It was an utter waste of time because the driver and his mates had fibbed about their driving, insisting they were not going faster than the regulation 40mph despite they’d been in the suicide lane not the granny lane.

It all cost Plessey a small fortune and the cost of a wrecked HDRS container.

I recall the findings backed up the ruling to stick to 40mph.

But all that’s a world away now apart from the Skanti radio in my workshop which (alas) brings back memories whenever I enter the door!

Allan G3PIY

 


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of Mike
Sent: 13 November 2020 15:50
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

In the day job before retirement, we did a lot of design work for the MoD, including organising all the various trials.  Interestingly, the worst spec for vibration was for tracked vehicles.  (With the possible exception of submarines being depth charged)  The tracked vehicle specs were really severe and quite a lot of kit came back from initial trials in kit form.  Then of course we had to do EMP tests, and I don't mean from lightning…  There was a test facility at Farnborough but that's gone now I believe.  I bet the local Amateurs hated that when it 'fired'!  Amazing place.

 

73, Mike,

Mike Stevens,

G8CUL/M0CUL/F4VRB.

 


Mike
 

Hi Allan,

 

I've only been away from the day job for 3+ years so it's all still quite fresh.  Since I left, all the engineering team bar one have now left as the new owners decided that they'd keep all the engineering work with them - in the South of France!  We did some great work, having fun at the same time.

 

One job was to fit some in-house designed C&N training equipment on a 'Fox' vehicle (Fuchs in German I believe).  This was a big 6 or 8 wheeled vehicle and of course we needed one at our place to fit the kit.  Just to make sure the batteries didn't go flat we had to run the engine up and have a short drive around the site.  Shame.  It was amazing how everything else got out of our way.  After deployment we had to do a firmware upgrade while the vehicles were deployed on exercise on the Salisbury training area (STA?).  In December.  I shall remember for a long time the drive across the plain after dark following another LandRover (I was driving a military spec one too) with no lights on except the convoy light underneath.  Funny how nobody else wanted to drive that day!

 

Great fun and I got paid for it too.

 

Thanks for your restoration write-ups, especially the current B62 (B40) one.  I remember back in the 60's a lot of that sort of kit for sale in the WS shop in Oxford, particularly B40s stacked up for sale.  If only….  I do enjoy reading your reports and I find them an inspiration to get the AR88 I have back to running condition.  One day.

 

73, Mike,

Mike Stevens,

G8CUL/M0CUL/F4VRB.

Moderator's Note: Salisbury Plain Training Area = SPTA.

 

From: wireless-set-no19@groups.io On Behalf Of AllanIsaacs
Sent: 13 November 2020 16:05
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Maybe you got involved with HDRS Mike, maybe not but one of our containers rolled on the M6 and MoD insisted on an independent full trial somewhere in the SE.

It was an utter waste of time because the driver and his mates had fibbed about their driving, insisting they were not going faster than the regulation 40mph despite they’d been in the suicide lane not the granny lane.

It all cost Plessey a small fortune and the cost of a wrecked HDRS container.

I recall the findings backed up the ruling to stick to 40mph.

But all that’s a world away now apart from the Skanti radio in my workshop which (alas) brings back memories whenever I enter the door!

Allan G3PIY

 

 


Mike
 

" Moderator's Note: Salisbury Plain Training Area = SPTA."

 

Yes, of course it is - thanks.  It's amazing how quickly these details are forgotten!

 

73, Mike,

Mike Stevens,

G8CUL/M0CUL/F4VRB.

 

 


Virus-free. www.avast.com


AllanIsaacs
 

Yes, Salisbury Train Playing Area; at Plessey Southleigh we had about 20 band new diesel Land Rovers with delivery mileage to play with. They must have been parked up for the best of a couple of years with regular battery charging.

Each had loads of ballast for towing the HDRS containers and they were so noisy it was virtually impossible to drive them without ear protectors.

 

The AR88 isn’t too bad to work on except for nasty oil leakage and their dead weight.

 

We once had a job from MoD where a couple of Plessey lads had to visit a mock-up village on the Salisbury Plain. Name escapes me, but it was supposed to feel like NI. Their actual job amongst other things was to get fired at by snipers aiming to miss by a foot or so. They didn’t seem to mind, it was in the good old days before H & S and I remember it got them off Jury Duty.

Allan G3PIY

 
Moderator's Note: probably Imber Village.


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of Mike
Sent: 13 November 2020 16:38
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Hi Allan,

 

I've only been away from the day job for 3+ years so it's all still quite fresh.  Since I left, all the engineering team bar one have now left as the new owners decided that they'd keep all the engineering work with them - in the South of France!  We did some great work, having fun at the same time.

 

One job was to fit some in-house designed C&N training equipment on a 'Fox' vehicle (Fuchs in German I believe).  This was a big 6 or 8 wheeled vehicle and of course we needed one at our place to fit the kit.  Just to make sure the batteries didn't go flat we had to run the engine up and have a short drive around the site.  Shame.  It was amazing how everything else got out of our way.  After deployment we had to do a firmware upgrade while the vehicles were deployed on exercise on the Salisbury training area (STA?).  In December.  I shall remember for a long time the drive across the plain after dark following another LandRover (I was driving a military spec one too) with no lights on except the convoy light underneath.  Funny how nobody else wanted to drive that day!

 

Great fun and I got paid for it too.

 

Thanks for your restoration write-ups, especially the current B62 (B40) one.  I remember back in the 60's a lot of that sort of kit for sale in the WS shop in Oxford, particularly B40s stacked up for sale.  If only….  I do enjoy reading your reports and I find them an inspiration to get the AR88 I have back to running condition.  One day.

 

73, Mike,

Mike Stevens,

G8CUL/M0CUL/F4VRB.



 

That’ll be Imber

 

From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of AllanIsaacs
Sent: 13 November 2020 17:32
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Yes, Salisbury Train Playing Area; at Plessey Southleigh we had about 20 band new diesel Land Rovers with delivery mileage to play with. They must have been parked up for the best of a couple of years with regular battery charging.

Each had loads of ballast for towing the HDRS containers and they were so noisy it was virtually impossible to drive them without ear protectors.

 

The AR88 isn’t too bad to work on except for nasty oil leakage and their dead weight.

 

We once had a job from MoD where a couple of Plessey lads had to visit a mock-up village on the Salisbury Plain. Name escapes me, but it was supposed to feel like NI. Their actual job amongst other things was to get fired at by snipers aiming to miss by a foot or so. They didn’t seem to mind, it was in the good old days before H & S and I remember it got them off Jury Duty.

Allan G3PIY

 
Moderator's Note: probably Imber Village.



MichaelBuckley
 

Depends opn d ate as there is now a separate NI type villiage, used for Urban fighting Trg

Mike

On 14/11/2020 10:54, Robin_Birch wrote:

That’ll be Imber

 

From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of AllanIsaacs
Sent: 13 November 2020 17:32
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Yes, Salisbury Train Playing Area; at Plessey Southleigh we had about 20 band new diesel Land Rovers with delivery mileage to play with. They must have been parked up for the best of a couple of years with regular battery charging.

Each had loads of ballast for towing the HDRS containers and they were so noisy it was virtually impossible to drive them without ear protectors.

 

The AR88 isn’t too bad to work on except for nasty oil leakage and their dead weight.

 

We once had a job from MoD where a couple of Plessey lads had to visit a mock-up village on the Salisbury Plain. Name escapes me, but it was supposed to feel like NI. Their actual job amongst other things was to get fired at by snipers aiming to miss by a foot or so. They didn’t seem to mind, it was in the good old days before H & S and I remember it got them off Jury Duty.

Allan G3PIY

 
Moderator's Note: probably Imber Village.



AllanIsaacs
 

Not really “Tuning Problems” That aspect has now been solved to my satisfaction. Thanks to all…

Scroll to near the end…

http://www.radiomuseum.co.uk/Murphy62brepair.html

 

Imber does ring a bell. Here’s something that would just get lost in the mists of time….

We were testing a sniper detection equipment called IA2 built into flak jackets and using a remote radio beacon… but it wasn’t accepted in the end because of new H & S rulings which effectively meant that a soldier (or his relatives) could sue HM if he got shot whilst wearing the equipment.

That meant MoD was happy the same soldier not wearing the equipment could get shot and not have a claim.

A bit odd really because IA2 would usually give the soldier a fighting chance if he wore the equipment and the sniper had missed with his first shot.

If he was not wearing IA2 he’d probably get shot at the second attempt.

 

The key technical problem was reflections from (Imber) buildings when the soldier might dive for cover on the wrong side of a wall.

Even if IA2 gave him a 50% chance, surely it would be better?

 

Eventually the kits were dismantled and the detectors fitted on poles on top of police stations with the displays inside at the front desks.

It was said at the time that some members of the public gathering outside police stations had a hat fitted with a large arrow on the top.

 

I understand Racal came up with a kit using Doppler and microwaves but whether it got into service I don’t know?

In the end however, sniper locations were usually known to soldiers and they just avoided them.

Allan G3PIY

 

 


Michael O'Beirne
 

Alan

 

A combination of excessive H&S and ambulance chasing lawyers chasing large fees have put the MoD on the defensive at nearly every turn.  

 

In offensive operations there is always a high element of risk.  Technology such as Kevlar helmets and vests can lower some of the risk but high tech in the field has to be strong and is yet another embuggerance load to cart about and probably to get damaged.  Things with batteries are inherently unreliable.

 

Good planning, good eyesight, basic common sense and experience will take you far.

 

73s

Michael

G8MOB

 

From: wireless-set-no19@groups.io <wireless-set-no19@groups.io> On Behalf Of AllanIsaacs
Sent: 14 November 2020 11:32
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Tuning problems

 

Not really “Tuning Problems” That aspect has now been solved to my satisfaction. Thanks to all…

Scroll to near the end…

http://www.radiomuseum.co.uk/Murphy62brepair.html

 

Imber does ring a bell. Here’s something that would just get lost in the mists of time….

We were testing a sniper detection equipment called IA2 built into flak jackets and using a remote radio beacon… but it wasn’t accepted in the end because of new H & S rulings which effectively meant that a soldier (or his relatives) could sue HM if he got shot whilst wearing the equipment.

That meant MoD was happy the same soldier not wearing the equipment could get shot and not have a claim.

A bit odd really because IA2 would usually give the soldier a fighting chance if he wore the equipment and the sniper had missed with his first shot.

If he was not wearing IA2 he’d probably get shot at the second attempt.

 

The key technical problem was reflections from (Imber) buildings when the soldier might dive for cover on the wrong side of a wall.

Even if IA2 gave him a 50% chance, surely it would be better?

 

Eventually the kits were dismantled and the detectors fitted on poles on top of police stations with the displays inside at the front desks.

It was said at the time that some members of the public gathering outside police stations had a hat fitted with a large arrow on the top.

 

I understand Racal came up with a kit using Doppler and microwaves but whether it got into service I don’t know?

In the end however, sniper locations were usually known to soldiers and they just avoided them.

Allan G3PIY

 

 

_._,_._,_