Discussion in 'Amplitude Modulation' started by KK6VQK, Nov 29, 2019.
Pish, those people may be too young to want to do 2m AM.
(Also, I wonder if my 706mkiig will do 2m AM..)
I worked some people on 6 meter AM with my icom 7300 into a fan dipole that had a 6 meter element.
I suppose height is very important and I have none really...40 feet tops...
I have an HA460 that works fine but it needs a xtal if you wanted to not drift around the band...
Most modern radios support 6 meters...
Oh i know about 6m. I have a TS-690 that I use on 6m, complete with a hamstick dipole on a rotor because I'm lazy. I was just curious about 2m AM on this old hallicrafters SR-42.
And yeah, the SR-42 has crystals for transmit, and an internal VFO that's only used for receive. I figure this is due to ye olde rules.
I'm just trying to find excuses to wire up the old tube radios for some temporary fun.
Which "olde rules" are you referring to?
There were VERY few of the "olde tyme" AM VHF units that had a transmit VFO. There were no regulations about this. Such was because, in those days, getting an actually stable VFO was VERY difficult. Therefore, the built in transmitters were crystal controlled. Several manufacturers did have separate VFOs available and even then most of these units were just passable for AM phone.
The only legal requirement for crystal control was before 22 November 1968 (when incentive licensing came into being), Novice Class operators had phone privileges in the 145.0 MHz to 147.0 MHz segment. The regulations allowed 75-watts input power and crystal control.
Mine is an SR-42A, which I think is on or around 1968. But yeah ,your point about stable VFOs for VHF work is well taken.
Ive overhauled a SR-42 and RX stability is quite good on AM after an hour. Also have the matching SR-46 and external HA-26 6 and 2M TX VFO.
The TX audio is superb.
Originally, horizontal polarization was preferred for AM mobile because it was less subject to ignition noise. Became sort of a moot point after the advent of FM. For DX work, there might still be a slight advantage with horizontal polarization
Another reason to use horizontal would be that depending on your area, a lot of people might also work SSB on 2m and want to use the same multi element antenna on AM as they use on SSB.
Back in the 70's in SOCAL, I used a Heathkit "Twoer" on AM and all the people I was talking to used their Cushcraft 11el beams that they also used on FM so they were all vertical.
After moving into the Central (San Joaquin) Valley, I noticed that anyone wanting to get on AM were more likely to use horizontal. (I had a horizontal 19element Hygain "LongJohn" @70ft)
In either case, for long haul LOS work, the difference can be as high as 27db if you're using a vertical multi element beam to "talk" to a horizontal.
I now have a Hallicrafters SR34 that I would to get on 144.4 AM with in the PNW. I don't know what people are using here but before I put up an antenna, I'll ask some of the regulars what they're using.