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 Post subject: what type of HRO do I have here?
PostPosted: Nov Wed 15, 2017 11:18 pm 
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Joined: Apr Mon 24, 2006 3:01 pm
Posts: 624
Location: Lombard, PA
I just picked up an HRO from an estate, but I'm not an expert on this radio and am kind of lost. It's in just superb shape and has obviously had a number of mods done to it. For one thing, it's got a tube compliment like none I can find - it includes a Western Electric 717 as, I guess, an RF amp. It's even got a transistor where a tube normally goes. There is no 6V6 in it. Underneath, there's a Calrad audio module along come front panel controls I've never seen on any other HRO. It also has a set of 9 coils, from 50khz to 30 meg.

IN the pictures, you can see the red, lighted switch on the left. This is main power. The headphone jack is on the right and there's a switch labeled ANL - which does seem to cut noise. The left blue control seems to fine tune and I don't know what the right one does, but I suspect it's used in SSB reception. INside, this is a work of art - whoever did this knew what he was doing. The work is factory quality.

This has an internal power supply and powers up fine. I tried it on the broadcast band and headphones today and got great audio with only a six inch piece of wire. Oh yes, a light was added above the tuning knob. There is no serial or model number on the chassis or anywhere that I can find.

Also note the rectangular box on the right side of the chassis - It's got what could be two crystals plugged into it. I've never seen this on any HRO pictures.

So does anyone have a clue about this?

Also, can someone explain the coils - these are marked "for use with RC-105 Receiver." I believe this was a Coast Guard designation. Why do some coils I see have two bands and these only have one?

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 Post subject: Re: what type of HRO do I have here?
PostPosted: Nov Wed 15, 2017 11:39 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 4810
That is a HRO Senior produced for the Coast Guard under model RC-105, early 1940s most likely date period. It has at least some modifications with the front panel switches added.

Rodger WQ9E


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 Post subject: Re: what type of HRO do I have here?
PostPosted: Nov Thu 16, 2017 12:15 am 
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Joined: May Fri 01, 2015 2:33 am
Posts: 957
Location: Roslyn,Pa 19001
Hi,
What you have is a highly modified war time HRO '42-'45 model. Where to start... Originally it never had an inboard p/s, transistorized local osc, 717 tube for the 1st rf amp. Looks like the xtal filter has been changed to some sort of bandpass job.
The differences in the coil units are because some are bandspead coils and others are general coverage. Great tutorial here:
http://www.radioblvd.com/National%20HRO.htm

Terry N3GTE


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 Post subject: Re: what type of HRO do I have here?
PostPosted: Nov Thu 16, 2017 1:52 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2964
Location: Seattle WA US
That coil set Number 1, 190-450kc is for a RAS receiver having a 175KC IF frequency. The seller must have included it just to jack up the coil count.

You have a Frankenradio in a HRO cabinet. The serial number of the original hro is probably on the chassis underneath the added power transformer.

-Chuck


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 Post subject: Re: what type of HRO do I have here?
PostPosted: Nov Thu 16, 2017 3:13 am 
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Joined: May Fri 01, 2015 2:33 am
Posts: 957
Location: Roslyn,Pa 19001
+1
The proper coil unit for the HRO on that band would cover 180-430kc. National left a 50kc non coverage area near the if frequency (456 or 455kc depending on the year it was made). As far as I know all of the RAS coil sets have those riveted on chrome bits at the end of the front, it's part of the locking mech that is only used on the RAS.

Terry N3GTE


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 Post subject: Re: what type of HRO do I have here?
PostPosted: Nov Thu 16, 2017 2:58 pm 
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Joined: Apr Mon 24, 2006 3:01 pm
Posts: 624
Location: Lombard, PA
Thanks to everyone who replied! I went and looked and the coil for 190-450 is marked "for RAS-2 Radio" just as you said. The others are all marked "for RC-105", so I guess these are right for this radio.

The mods to this are surprising in scope and number - a power supply added, new RF amp, new transistorized local oscillator, new audio output, likely something to work better with SSB signals, a new noise limiter and probably other things. Someone went to a LOT of trouble - hopefully the radio is better for it, though I'd rather they'd have modded one not in such good condition.


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 Post subject: Re: what type of HRO do I have here?
PostPosted: Nov Sat 18, 2017 2:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 7473
Location: Beaver Falls, PA. USA
Look through issues of CQ and QST from the late 50s and early 60s; the conversion documentation might be there.

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Tim KA3JRT


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