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Old 28th Aug 2018, 1:36 pm   #81
ms660
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Default Re: HRO and BC348

Some BC348's did survive with an ID plate, here's my old one, a Q version by Wells Gardner, amazingly enough it had its original dynamotor fitted.

Lawrence.
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Old 28th Aug 2018, 5:17 pm   #82
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Default Re: HRO and BC348

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Some BC348's did survive with an ID plate,
Lawrence.
As did mine, a BC348O. Never butchered.
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Old 28th Aug 2018, 5:46 pm   #83
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Default Re: HRO and BC348

That's a nice example, shock mount too.

Lawrence.
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Old 28th Aug 2018, 5:50 pm   #84
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Default Re: HRO and BC348

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Originally Posted by M0SOE_Bruce View Post
Quote:
Originally Posted by ms660 View Post
Some BC348's did survive with an ID plate,
Lawrence.
As did mine, a BC348O. Never butchered.
All mine, but one has the I.D. plate.
I see, both of you have the original speaker. I have one that the plate states "Heppner Mfg Co."
All my sets had the Dynamotor removed and some form of A.C. power supply fitted. I installed an extra first audio stage to increase the volume, per one of the conversion manuals, that were out at the time.
Also, it seemed that all the shock mounts were MIA. I only have one on my best example.
Dave, Midwest USA.
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Old 28th Aug 2018, 6:28 pm   #85
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Default Re: HRO and BC348

I spy......

Just for a bit of fun, what else can anyone identify in the photo's I posted that's radio related, apart from the BC348 there are 5 other items in the 1st photo and apart from the BC348 and the LS-3 loudspeaker there are 4 other items in the 2nd photo.

One of them might be a bit of a pig to identify, I'm still not sure with one of them but I once did get a pointer to the manufacturer.

Lawrence
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Old 28th Aug 2018, 6:38 pm   #86
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Default Re: HRO and BC348

An HRO and possibly a CR-300 receivers?
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Old 29th Aug 2018, 12:34 am   #87
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Default Re: HRO and BC348

I have been looking through my old QSTs from the '30s and '40s and the HRO design seems very interesting.
When it was released in 1935 it already looked out of date. But it was manufactured for another 10 years in more or less the same form, and it was copied in several other countries. Why?
The plug-in coils were the main point of difference. By 1935, other radios were appearing with bandswitching and direct frequency readout, which you might imagine would kill off an HRO-type design.
Evidently National had plenty of customers who didn't mind plugging in coils and reading little graphs. A lot of the commercial customers probably used only one or two frequencies anyway. Radio amateurs had all the time in the world, of course.
Having coils which were plugged in 'sideways' was a stunning innovation. it meant you had space to mount those little graphs, and you could reduce the overall depth of the radio. The tradeoff was the need for an east-west main tuning capacitor, and therefore for a rather complex gearbox and dial. National did such a good job of this that they sold them to the HRO clone-makers as a standalone component. Even today these capacitor/gearbox/dial assemblies turn up at junk sales in New Zealand, 'new old stock'. They were probably left over from production of clones by local manufacturer Collier and Beale. Now they change hands for a few dollars.
Also absent in the HRO was the PSU and loudspeaker. The cabinet was small but it was nice and cool in there. As we now know, lots of HROs were used in
WW2 monitoring stations, dozens at a time, so they could use common power supplies.
Before the Collins TCS series came along, they were also standard kit in small naval craft like LSTs. This would be a severe test for any radio. My guess is that the sheer simplicity of the HRO, and its build quality, made it a very reliable and serviceable item, and thus favoured by the military.
Note that the HRO was never a cheap radio. In 1940 only the Hammarlund Super Pro was more expensive.
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Old 29th Aug 2018, 5:44 am   #88
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Default Re: HRO and BC348

The gearbox in the HRO exploits the right angle requirement by being only a single stage worm and wheel type, which offsets some of the costs.

Everyone bangs on about the scale length of the HRO, but the HRO has TWO scale lengths. Ten times round that disc on the tuning knob gives superb re-settability, but the poxy little graphs give damn-all resolution in frequency. So you may not know very well where you are, but you can definitely return with accuracy.

Could this be why there seems to have been so many BC221s around?

David
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Old 29th Aug 2018, 5:48 am   #89
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Default Re: HRO and BC348

Iíve always thought an HRO would be a prime candidate for a digital readout mod.

Jim
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Old 29th Aug 2018, 9:33 am   #90
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Default Re: HRO and BC348

A frequency counter anywhere in the same room should do the trick!
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Old 29th Aug 2018, 10:36 am   #91
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Default Re: HRO and BC348

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An HRO and possibly a CR-300 receivers?
Yes, spot on, HRO in 1st and 2nd pic, Marconi CR300 in 2nd pic, 6 more radio related items to identify from the pics......

Lawrence.
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Old 31st Aug 2018, 1:42 pm   #92
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Default Re: HRO and BC348

No more takers so here goes.

1st photo: Top left: Avo CT378a signal generator...Middle left: Murphy B40d receiver...Bottom: Eddystone 358x receiver...Middle right: Hallicrafters SX28 receiver cabinet.

2nd photo: Bottom right: Marconi Type 889 power supply...Bottom left: Not sure on this one, it's a loudspeaker cabinet of I believe USA origin, metal Art Deco type metal strips on the top (two of) I no long have it but from memory it had a fancy H scroll on the front panel (panel was wood stained black) not a Hallicrafters H though, but someone once said it was used with a Howard receiver? the main cabinet was metal, open back and finished in black so far as I remember, I posted a photo of the loudspeaker cabinet on a forum some years ago for ID (might have been this forum) If I can find it I'll post a link.

Lawrence.
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Old 31st Aug 2018, 2:13 pm   #93
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Default Re: HRO and BC348

Ref post 92, the H can only be assumed if the cabinet is on its side 'cos I've just found a couple of photo's, will do a separate ID thread in Components and Circuits.

Lawrence.
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Old 1st Sep 2018, 11:50 am   #94
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Default Re: HRO and BC348

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Originally Posted by Radio Wrangler View Post
The gearbox in the HRO exploits the right angle requirement by being only a single stage worm and wheel type, which offsets some of the costs.

Everyone bangs on about the scale length of the HRO, but the HRO has TWO scale lengths. Ten times round that disc on the tuning knob gives superb re-settability, but the poxy little graphs give damn-all resolution in frequency. So you may not know very well where you are, but you can definitely return with accuracy.

Could this be why there seems to have been so many BC221s around?

David
My understanding was that the US "heavies" each had a BC221 on board as part of the standard kit and that there was quite a thorough and intensive rigmarole of calibration run-through of the various (and steadily increasing in number!) radio devices on board as part of the radio operator's pre-flight checks, and that the 'HT out' provision on the BC348 was to run the BC221, LT being provided by a amall 6V lead-acid battery on the BC221 bottom shelf. That could be one explanation for quite a few RX and TX devices having provision for a low-current 'HT out' provision. What with the BC221 adding to all the clobber on board, plus the alternative hefty PA tuning blocks for the BC191 etc. it's almost surprising that there was much room or payload left for bombs and all those crewmen!

I suppose that just about everywhere there was a requirement for high-resolution radio monitoring, there was a wave-meter reference present and the BC221 seems to have become the most numerous, hence its ubiquity- the story of its mass-production and automatic calibration is fascinating in itself.

Of course, a highly-resolving and versatile digital read-out module is beer-money nowadays, but the challenge becomes minimal-disturbance LO sampling with good reverse-isolation from digital sharsh,

Colin
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Old 1st Sep 2018, 12:17 pm   #95
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Default Re: HRO and BC348

Very stable the BC221 too after warm up.
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Old 1st Sep 2018, 2:37 pm   #96
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Default Re: HRO and BC348

Airbourne use was not the actual BC221 but the airbourne version whose designation escapes me. I had one a few years ago and it had a multi way connector on the side for power etc. Functionally identical to the 221.
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Old 1st Sep 2018, 4:21 pm   #97
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Default Re: HRO and BC348

The airborne freq meter was the LM series for US aircraft. The RCAF used the Canadian Marconi C2 frequency meter. It's function was similar but had direct readout, no need for calibration chart.
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Old 1st Sep 2018, 8:57 pm   #98
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Default Re: HRO and BC348

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Airbourne use was not the actual BC221 but the airbourne version whose designation escapes me. I had one a few years ago and it had a multi way connector on the side for power etc. Functionally identical to the 221.
I believe the BC-221 was frequently used, I've seen lots of pictures showing it. There was also the version you mention, without the battery compartment. I have an example, I'll check on its type number, my shed is now locked up.

Andy
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Old 1st Sep 2018, 8:59 pm   #99
M0FYA Andy
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Quote:
Originally Posted by M0SOE_Bruce View Post
The airborne freq meter was the LM series for US aircraft. The RCAF used the Canadian Marconi C2 frequency meter. It's function was similar but had direct readout, no need for calibration chart.
The BC-221 was used by the USAAF, whereas the LM series were used in the Navy aircraft.

Andy
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