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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 3rd Aug 2018, 5:57 pm   #41
ms660
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Default Re: HRO and BC348

So far as I can make out the chassis braiding to the top cap screen of the 1st IF valve was fitted to the later all glass models eg: models M and MX that had the Xtal fitted inside the phasing box, the earlier types had a plug-in Xtal that plugged in to the top of the phasing box, I remember taking the Xtal out on my plug-in one to give it a clean.

You can see the braiding in the HRO M topside chassis layout in this manual:

http://www.cryptomuseum.com/df/hro/files/hro-5.pdf

Lawrence.

Last edited by ms660; 3rd Aug 2018 at 6:03 pm. Reason: Link added
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Old 3rd Aug 2018, 6:15 pm   #42
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Default Re: HRO and BC348

Interesting, either I have one with an internal crystal or I have just the box having the internal crystal as a spare. Evidence long gone if it is the latter.

Will remember to look at it next chance I have.

Yes washing the crystal from the plug in one is usually beneficial.

It's also instructive to pick off some IF from the box and feed it into a DSP dongle
SDR. Set for 1 MHz bandwidth it shows very nicely how well the coil box tracks across the dial. If the noise bump stays centred on 456k across the whole range you are doing well.

One of mine crossed over completely.
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Old 3rd Aug 2018, 6:25 pm   #43
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Default Re: HRO and BC348

Another give away that it's a later all glass valve job is the pressed steel gearbox cover, early ones were cast.

Lawrence.
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Old 3rd Aug 2018, 6:31 pm   #44
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Default Re: HRO and BC348

Well spotted.

Have you done any alignment of coil boxes? I have no idea how they did that.

The obvious capacitors are not hard to tune with the right tool but swinging the loop in
the middle of the coil former to set inductance? Only a brave man would try that with the HT on!
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Old 3rd Aug 2018, 6:55 pm   #45
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Default Re: HRO and BC348

My front panel

Someone asked about bandspread...yes, I have a few bandspread coil packs including what I am told is a rarity...one for 15m.
Not all of my coil packs work - the topband one for example is known to be u/s and they may be others. I haven't yet had a chance top even try them all, let alone try to open them for fixing.

David
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Old 3rd Aug 2018, 6:56 pm   #46
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Default Re: HRO and BC348

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Originally Posted by Jon_G4MDC View Post
Well spotted.

Have you done any alignment of coil boxes? I have no idea how they did that.

The obvious capacitors are not hard to tune with the right tool but swinging the loop in
the middle of the coil former to set inductance? Only a brave man would try that with the HT on!
Yes, I've tweeked coil boxes, just C though not L.

The one I used the most was what I call the HRO Senior (plug-in Xtal) nice receiver, it was my favourite if I'm honest, always been a fan of the HRO receiver, it's a nice elegant simple design, that receiver had it's original set of four (1.7-30MHz) matched serial number (to the receiver) band spread coil packs so was really good for the amateur bands, for other general SWLing I had a Reception Set R106 MKII (HRO 5t) that had a full set of non bandspread coil packs that covered 50kHz-30MHz

Lawrence.
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Old 4th Aug 2018, 10:54 am   #47
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Default Re: HRO and BC348

Hi I did do some coil setups as per this write up. But to be honest I have re-read it several times this morning and I cant get my brain on the right wavelength!!! It did work effectively as I recall as originally I could not get the coil to track in by trial and error adjustment. National must have had a systematic approach but would not be dealing with coils designed and tracked for one model being used on another as many of us are. Lucky is the person with matching serial numbers!!

There is also a link in the thread from Andrew giving more of the maths behind these coils.



https://www.vintage-radio.net/forum/...d.php?t=111382

Pete
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Old 7th Aug 2018, 6:33 am   #48
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Default Re: HRO and BC348

Some of the BC348's had a built in power supply. Be sure to add a fuse to it.

The one I have came with a note in what had been the PS compartment telling me that the PS had shorted out and the radio had caught fire. No fuse was ever designed into the PS.
Also note that the round cap cans that look like a little "pot" with mica or micarta on the top are failing a lot. If you decide to keep it, I would suggest re-capping. They contain paper dialectric caps and the acid in the paper is causing them to fail.

All in all a pretty good for its time, and very rugged receiver.
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Old 7th Aug 2018, 11:36 am   #49
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Default Re: HRO and BC348

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Originally Posted by G3VKM_Roger View Post
The G2MI marking may not mean that the holder owned your HRO but it might be a reference to the logging scale setting of that receiver on 3650kHz. G2MI in Bromley (erstwhile RSGB President) used to read the RSGB news and Log scale 337.5 could have been 3650, a likely freq for the news. Stick a sig gen on it and see what the dial reads!
David, did you check to see if that dial reading corresponded with 3650kc?

73

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Old 11th Aug 2018, 4:15 am   #50
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Default Re: HRO and BC348

No Roger, Ive been busy and distracted by a friend's death.
I shall have a look today though, thanks for the reminder

David
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Old 11th Aug 2018, 6:27 am   #51
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Default Re: HRO and BC348

Very sorry to hear that, David. I don't have a "classic" HRO yet (although I'm getting one in October) so I can't make a measurement myself. I expect there's little difference between the dial readings of individual sets?

73

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Old 21st Aug 2018, 8:55 am   #52
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Default Re: HRO and BC348

I have looked at those numbers as freqs vs dial.readings (or graph plots, anyway) and they dont seem to be. The coil pack doesnt function as it should now...it wont go low enough in frew. Its a 3.5mhz pack but wont go below about 3.7ish

So even if the numbers did once correlate, they dont now.

David
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Old 21st Aug 2018, 6:07 pm   #53
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Default Re: HRO and BC348

This is not so unusual. If you have matching Ser#s between coil pack and set it is quite sad.

I have been looking back in the post and now I am lost as to whether this G2MI logging is on a bandspread or a general coverage setting. As it was 3755 dial (I think!) suspect bandspread.

So many things affect HRO Cal. The one that I battle is the insulated rod on which all the moving vanes sit. The vanes are set by pairs of grub screws but they bite into the rod and leave indents. If you want to re-cal all four gangs of that capacitor what do you do? Rotate by 90 and start again with a capacitance meter?

I have had sets where someone had rocked the LO gang. All the RF stage ones at max C but LO not quite. I thought that was suspect - or it could be deliberate...?
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Old 21st Aug 2018, 6:36 pm   #54
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Default Re: HRO and BC348

I wonder how long the design team thought these sets would last...
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Old 21st Aug 2018, 6:41 pm   #55
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Default Re: HRO and BC348

Some literature says HRO should have been HOR - Hell Of a Rush.
Nobody would buy a receiver called a HOR - er?

Any truth in it? I don't know but it could explain these small niggles.

As we are discussing it 80 years after, it can't have been that bad.

And a later edit - what happened to the BC348 contributors
They are not the same - on some things the HRO wins - on others the '348.
For a fanatic radio operator's set I will say HRO wins.
For a casual radio operator I will award the '348. And that is how the designers meant it to be.

Must get my BC348 out again..

Last edited by Jon_G4MDC; 21st Aug 2018 at 6:53 pm. Reason: weighing fair
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Old 22nd Aug 2018, 12:37 pm   #56
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Default Re: HRO and BC348

Interesting comments Jon. I do like listening to my HRO although it makes a heck of a noise as it picks up all the qrm never dreamed of in 1939. My BC348 sits next to it so I ought to use it more. But then I ought to use my 1155 more too...

D
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Old 22nd Aug 2018, 12:48 pm   #57
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Default Re: HRO and BC348

Time we all had a Vintage Rig day and fired up what we have either for tx or rx?
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Old 22nd Aug 2018, 12:55 pm   #58
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Default Re: HRO and BC348

The HRO's I owned were very well made, they were well thought out and designed (Millen, Hoover etc) I don't think they were built in a "rush" they would have left the factory with the alignment spot on, the rotor sections on the tuning gang should all be in line, the outer rotor plate being tweeked for fine adjustment, over the years many have been got at and fitted with go faster modifications etc.

Lawrence.
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Old 22nd Aug 2018, 1:46 pm   #59
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Default Re: HRO and BC348

Agreed Lawrence,inc the wrong valves and bases!
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Old 22nd Aug 2018, 2:40 pm   #60
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Time we all had a Vintage Rig day and fired up what we have either for tx or rx?
Through FISTS I am arranging this



Chirp ‘n’ Drift 2018

1800Z Friday 2nd November to 0100Z Saturday 3rd November this year is the Chirp n Drift event. The Dam Busters activity a few months ago was just too much fun to be allowed to go away for ever. I think that on the Friday night there are no contests (is there EVER a night with no contests??), the kids will be in bed, the work will be finished and the weather too rubbish to be out, so…fire up the crystal / valve gear, warm up the vintage wartime stuff and lets have another bash. Open to all, obviously, it is nothing more than a focal point for vintage operators. Spread the word, pass the details and lets have fun. (FISTS...Comments / logs can be submitted but no special exchanges required.)
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