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Reviews Categories | Receivers: General Coverage | National HRO500 Receiver Help


Reviews Summary for National HRO500 Receiver
National HRO500 Receiver Reviews: 6 Average rating: 4.0/5 MSRP: $1500.00
Description: National Radio's all-transistor HRO receiver from the early/mid 1960's with the unmistakable HRO dial.
Product is not in production.
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KM1H Rating: 4/5 Apr 18, 2010 08:28 Send this review to a friend
Ahead of its time  Time owned: more than 12 months
I'll start by saying that I worked for National in the Service Dept 1963-69 and spent countless hours with the HRO-500 and its problems and quirks. I still repair them for customers and todays problems are mostly quite different.

When released it was far ahead of the competition. It borrowed ideas from the AN/WRR-2 and FRR-59 military all tube radios as well as some not so good ham models.

While the germanium transistor overload is indeed true the front end switchable attenuator was put there for a reason. Many fail to notice it. Its function is the same as the switchable attenuator on most all modern SS radios and even the best of them require a BCB reject filter at times.

In any case the overload performance is about the same as the Collins 51S1 and the HRO-500 has far fewer internally generated "birdies".

Servicing one today requires replacing every electrolytic capacitor. There are 20 including the can and its a very simple job.

The resistors used are poor quality and many have drifted way up in value. This is a common theme in many Nationals starting in the late 40's when new owners put quality below the insistence of buying the cheapest outside vendor parts possible.

The transistor leads and sockets become corroded. Each one should be removed and inserted several times. Ive no use for DeOxit here as its way too easy to cause more problems. Save the DeOxit for switch contacts and use only the smallest amount possible on a toothpick. Rotate the switch several times and then wash off the residue with a quality product. I use fast evaporating brake cleaner and have also used CRC Electric Motor Cleaner. Whatever you use test its reaction first.

Many sets have SSB distortion due to a wiring error. This has been covered in ER Magazine and elsewhere....simple fix.

Even after all the above and an alignment the radio may still have performance problems. Germanium transistors have leakage from the beginning and it gets worse with age. Use the manuals voltage charts and get out a scope if necessary. This is not a radio to use cheap and useless test equipment on by the way. High quality older HP, Tek, Fluke, etc equipment is almost a give away these days.

Sensitivity on the higher bands can be improved with an external TUNABLE preselector with a high intercept device. Set the preselector gain just high enough to overcome the HRO's noise figure for the band of interest; experiment with the attenuator and preselector gain. Setting the gain too high does nothing except amplify noise and add to the overload. The HRO-500 also wants a 50 Ohm antenna if you are not using an external preselector. A piece of wire or open wire line fed antenna just wont cut it and will add to the problem. The Hi-Z input jack is inadequate for serious use.

Due to the LC VFO and crystal oscillators the synthesizer phase noise is far below all but the best of modern SS radios. Defective components and especially leaky transistors can make it very poor.

If you dont feel up to digging in then drop me an email, my 45 years experience of working on these is available. km1h@jeremy.mv.com

Carl
KM1H
 
CT1DGN Rating: 5/5 Oct 25, 2008 18:58 Send this review to a friend
A reference!  Time owned: 0 to 3 months
I started my ham activities at CT1TX home, living in a small town north of Portugal (Viana do Castelo). He had one of those great receivers, with robust construction, wonderful service manual!!! Remember that at that time (1965 the 1st issued)there was no strong competitor with a full solid state and such 1KHz dial resolution!
 
SWL377 Rating: 3/5 Oct 6, 2007 01:52 Send this review to a friend
just OK, but cool  Time owned: 0 to 3 months
I spent hours pondering this rcvr in the 80's. I had a chance to buy one in perfect operating condition maintained by a guy who specialized in repairing and aligning these sets. It looked a bit ratty, ex govt, but had zero operating faults. I could have bought it for $250 but passed after spending a lot of time listening to it and playing with it. I brought in a Sony 2001 to do comparisons and found in many cases that early Sony with all its synth noise could outperform the HRO 500. I also read about what a nightmare it is to change light bulbs in the 500. It was a neat looking set, but was a bit of a hassle to tune and didn't seem to be a low noise high sensitivity rcvr. I later saw a bunch of NIB ones come up for govt auction. They were in large quantity lots and went for a lot of money. I heard later that many NIB sets had faults right out of the box. I think relaibility was an issue with the 500. Still, those HRO rcvrs have the coolest radio tuning knobs in the universe.
 
K7NG Rating: 4/5 Dec 18, 2006 11:25 Send this review to a friend
Unique, limited  Time owned: more than 12 months
I had access to (but didn't actually own) a HRO-500 in the 1977-1979 time frame. During this period I spent a lot of time in front of the receiver and had good opportunity to observe it, for better or worse.

The receiver was unique for its' time in the design of the synthesized local oscillator. To be honest, I really think the LO performance wouldn't be thought of too badly even today. The LO was quiet and very stable. The many many LO ranges was due to the synthesis method. Remember that National in those days made a lot of military stuff and they borrowed some of the designs to make the HRO-500. The readout...well you had to know about where you were supposed to be and the fine resolution came from the HRO dial. The feel of the tuning knob was...HRO. They don't make 'em like that any more.
The rest of the receiver was - mediocre. Bipolar transistor RF amp and mixer...cross modulation was a common problem. BCB stations showed up here and there due to the X-mod plus minimal front end selectivity. Not real good on the audio quality, particularly on SSB.
Bottom line - I thought the receiver was a lot of fun to use, but I wouldn't want to count on it for applications that placed great demand on performance.
 
KA8DLL Rating: 5/5 Oct 23, 2006 07:22 Send this review to a friend
very nice radio  Time owned: more than 12 months
All chrome front, man size knobs , excellent construction,accurate dial,pass band tuning, variable selectivity, excellent notch filter. very pretty light blue case. Performance at least equal to a R390A. Truely a classic from the 60's.
 
KA9P Rating: 3/5 Apr 26, 2004 22:31 Send this review to a friend
Looks good, sounds OK  Time owned: more than 12 months
Someone had to review this wonderful old radio. Like many, the thrill of the hunt somewhat exceeds the experience of ownership. Having drooled since I first saw one in Trigger Electronics as a teenager, the chance came and I bit.

The radio I acquired had came straight from an ace HRO500 mechanic, and works flawlessly. Unfortunately, what you read about distortion on SSB is true, at least in this version, and it's not that pleasant to listen to on SSB. My 60 year old HRO-MX sounds wildly better with the gain turned down - turning the RF gain down on the 500 doesn't make the distortion go away. See Electric Radio for a purported fix to balance the detector xformer if you like to fiddle. AM is much better and sounds great through a big speaker.

These radios often have synthesizer quirks, but a properly aligned, properly functioning version locks right up with no fussiness whatever.

Unfortunately, the two speed dial drive is tiring to drive for long periods, so it's not a band scanner. But I'd do it again just for the chromed micrometer drive, and the feel of the hefty synthesizer setting knob. A neat piece of history, but not to die for if you only want to listen, especially to hams or ute's.
 


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