Simple way of getting on A.M.

Discussion in 'Amplitude Modulation' started by G3YRO, Mar 5, 2021.

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  1. W1BR

    W1BR Premium Subscriber QRZ Page

    I visited a local ham's estate last spring. His SP-600, Viking I and other homebrew rigs where there. Some elderly VHF rigs in the mix. Not a single crystal to be found. I think there is some black hole that swallows them up. Try and find a 8400 kc rock for six meters that isn't being held for a king's ransom :)
     
  2. N1BCG

    N1BCG Ham Member QRZ Page

    To many, a collection of crystals is little more that a reminder of the inconvenient pre-synthesized days. The impression is that they are also undesirable to others. That, and their small size, suggests little reason to put them up for sale online or at a hamfest.

    Only manufactured rigs and other "obvious" items are thought to be of any value to SK estates, so it's likely that they get tossed into the garbage with other bric-a-brac like 9 pin accessory connectors, 2 pin mic plugs, and crystal compartment covers for Rangers and Valiants.

    Basically, all the things I look for at hamfests...
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    It's interesting that so many American HF transmitters were crystal-controlled . . .

    Back in the 60s I didn't know anyone here in Britain that didn't have VFO-controlled Transmitters, whether Homebrew or Commercial.

    When I started building my own Transmitters when I got my Licence (aged 14), I never considered using a Crystal ! (not until I built an SSB Tx, and needed one for the Carrier Osc).

    Is it because your Novice Licence required you to be Crystal-controlled?

    Roger G3YRO
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That, plus all the old entry-level transmitters in the 50s and 60s didn't have VFOs, and buying an external one cost more money than several crystals cost -- back then!

    The NYC electronics (Army/Navy) surplus shops had thousands of crystals, mostly FT-243 holder type, they'd sell for a dollar each or less. So, we newbies who were mostly kids and had no money would buy some and use them. Many did fall inside the allocated U.S. "Novice" subbands.

    The popularity of xtal control created the norm of "tuning around" for replies to CQs.

    Fun days. I made many contacts with stations who weren't anywhere near my frequency.:p
     
  5. SM0AOM

    SM0AOM Ham Member QRZ Page

    In countries with multi-tiered licence systems, it was not uncommon to restrict Novices to crystal control only.

    This was derived from a general reasoning that the risk of transmitting put-of-band was much lower when crystal-controlled.
    Paired with lower power limits (often 5 or 10 W) it provided a strong incentive for upgrading.

    73/
    Karl-Arne
    SM0AOM
     
  6. G3YRO

    G3YRO Ham Member QRZ Page

    All we had in Britain was a Full Licence . . . or nothing !

    But around 1967 they introduced a B Licence - same Exam, but no Morse Test. You were then only allowed on 70cm and above.
    I only ever knew that practice on 2m and above (where most people WERE crystal controlled)

    Roger G3YRO
     
    Last edited: Mar 7, 2021
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    On VHF, a decent reason for xtal control was "stability," since most transmitters back then were all analog and used cascaded frequency multipliers, so a small amount of VFO drift became a large amount of frequency drift on VHF.

    But on HF, I still work (today) some stations using old gear and using xtal control. They mostly rely on having a decent enough signal when calling CQ that people will respond to them, since they can't zero-beat other stations.

    Just worked K0ZK, Arn in Maine, who was using an old Novice setup with xtal control on 40m CW. Heard his CQ, answered him.

    A lot of popular ham transmitters from the 50s and 60s had no VFOs. I think stuff like the DX-20, DX-35, DX-40, DX-60, T-60, HG-303, Globe Scout, Johnson Adventurer and Challenger and lots of stuff still "works" today and had no VFO unless someone added that. Back in those days, the VFOs might cost $35 to $99 and the cheap ones weren't all that stable. Today, a very stable (digital) synthesized VFO can be homebrewed for probably $20 plus an enclosure and power supply, but such technology didn't exist back then.

    I enjoy using old stuff when I have the opportunity.

    My own homebrew "AM" rig is a Handbook design from about 1960 (I think it was actually in the '57 Handbook) and uses a 4-250A plate modulated by P-P 811As, and the original design included a VFO which I never got working to be stable enough for me, so I chucked the VFO design and used a Hallicrafters HA-5 VFO, which is really quite stable and was $99 back in the 60s. They both still work fine. But I have a crystal for 3880 kHz and there are some AM nets around there, so if I want to "check in" fast without waiting for anything to warm up, I just use the crystal.

    The AM'ers tolerate some off-frequency operation and use wider filters and are willing to tune around slightly.
     

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