2m AM polarisation?

Discussion in 'Amplitude Modulation' started by KK6VQK, Nov 29, 2019.

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  1. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Or weak signal Communications such as ssb cw or am always use horizontal unless you're doing eme or satellite using cross polarization
    Horizontal is subject to less noise than vertical, that's why it's a preferred mode for weak signal activity
  2. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Yes it will
  3. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    way back (1970) when radios had pieces built out of rocks (crystals) , in London,ON there was a very popular AM net on 144.450Mhz.
    Most were using heathkit twoers. Almost everyone had 1/4wave verticals. Some of us who did work others outside of the local area all used horizondal beams. There were a couple of guys using transverters, few Cleggs, I had a heathkit pawnee (vfo) another fellow had a RME receiver with a 522 transmitter
    anyway as mentioned horz with a beam for distance and vertical for local
  4. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    On VHF, horizontally polarized antennas definitely work considerably better for "over the horizon" propagation. That is why horizontal polarization is used for weak signal work.

    Even back in 1960 when I first got on 2-meter AM, everyone used horizontal polarization. In those days, SSB operation was unheard of!

    Vertical polarization was used for 2-meter AM operation for short-range communications like some RACES nets. The earlier Gonset Communicators came with a quarter-wave "stinger" that connected directly to the SO-239 on the top of the unit. But, other than such operation, virtually every operator connected the coaxial cable from a horizontally polarized antenna to that connector.

    FM operation spilled over from the commercial two-way radio arena starting with the days that the old "super" wide-band equipment (i.e. Motorola FMTU-30D transmitter and FMRU-16V receiver, "coffin" radios) lost type acceptance and amateur radio operators started acquiring the units. Then, in 1962 a lot more commercial equipment lost type acceptance for low-band and high-band radios and in 1967 even public safety agencies had to go to the then "narrow-band" units.

    Since commercial operations were, primarily, for local area operation utilizing mobile units, vertical antennas were considerably easier to install on the mobile units and provided, basically, omni-directional coverage. As such, vertical polarization became the norm for commercial two-way operations. This carried over into the amateur radio realm and now virtually every amateur radio operator who operates on 2-meters and 70 cm uses FM and vertical antennas. However, for beyond r.f. line of sight operation, vertical antennas are definitely inferior to horizontally polarized antennas.

    Most man-made noise is vertically polarized. However, FM receivers incorporate limiter circuits to eliminate any AM component from the signal. Noise just happens to be an AM signal. Therefore, noise is greatly reduced by the limiter circuits and the FM receiver is, generally, not bothered by noise whereas any AM receiver (SSB is an AM signal) is definitely affected by noise.

    Glen, K9STH

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