Why are the old National radios with coil racks called "HRO"? Was it just
National's model number prefix or is HRO an abbreviation for something? And
what was it about the tuning mechanism that was supposedly so great? (That
tuning knob looks really cool).

RFCOMMSYS wrote:

Why are the old National radios with coil racks called "HRO"? Was it just
National's model number prefix or is HRO an abbreviation for something? And
what was it about the tuning mechanism that was supposedly so great? (That
tuning knob looks really cool).

There was series of radios with the HRO label. Some must date back to the 40's
all the way into the 70's with the HRO500 a great receiver

--
73 and Best of DX
Shawn Axelrod

Visit the AMANDX DX site with info for the new or experienced listener:

http://www.angelfire.com/mb/amandx/index.html

REMEMBER ON A CLEAR DAY YOU CAN HEAR FOREVER

The HRO tuning mechanism is a right angle gear drive with a 0 to 500 counter
built in to the knob and you can spin it,

Tnx JFR for the additiona and clarification.

Did the HRO have two or three stages of RF?

I has very little backlash because of pre-loaded gears

I seem to recall that all military comm gear of that period had those kinds of
gears. Each gear was a pair or "split" with a shared spring. The tension on the
gear teeth was obtained by rotating the gears in opposite directions and then
meshing them with the connecting gear or worm.

A popular military receiver was the BC-348 and BC-342. I forget which, but one
operated on 14 or 28 vdc and the other on 115 vac. The dc unit was easily
converted to ac.

Another colleague, a strictly CW operator, used one of those to rack up lots of
DX. That RX and a Meissner Signal Shifter feeding a war surplus 304TH was a
powerful and inexpensive CW station.

73,
Bill, K5BY