Icom 7610 and 705 AM review...

Discussion in 'Amplitude Modulation' started by N2DTS, Oct 5, 2021.

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    The 705 does not seem to have the bass hole on TX as well, it goes lower then the 7610 on RX and TX.
    It does not seem to modulate fully though.
    It stops on the TX side at 2900.

    The 705 RX is quite nice, no sync detection but good audio into headphones or an amplifier and good speaker, or even just into a good speaker.
    I have the A button on the microphone set to jump between vfo A and vfo B (80 and 40 meters).
    With the fan dipole, I can lump back and forth in 1/4 of a second...
    At 2 watts...or 60 watts into the RM italy amp...
  2. K5UJ

    K5UJ Ham Member QRZ Page

    That's too bad. There's more to ham radio than that. I sat for my Extra class test in 1975. I passed Advanced in '74 and General in '73. I was in high school and had no money for anything other than wires, a J36, T60 and crappy gen. cov. rx. But I could afford the $8 test fee to upgrade my license so that's what I did. Never regretted that.

    Same here but it wasn't decades ago. Jack K9ACT and I tried 20 a few times and had the exact same experience. One of us could hear someone the other couldn't. It sucks to sit there listening to band noise, about like trying to copy a piss weaker. I don't even bother with the high bands for phone. Every time someone says 15 or 10 is hot, I go up there and hear nothing. I'll call CQ and get nothing. Maybe unless the band is smoking hot like 1959, I need a beam. I can almost always raise someone on the low bands.

    I plead guilty. I could move my rig down there, but I'd have to tune the driver, the grid input network to the final, the output network and Matchbox. It takes around 15 minutes to QSY. I'm lazy and stay around 3880 but I should practice moving so I don't forget the procedure.
  3. WA3VJB

    WA3VJB Ham Member QRZ Page

    I get it. I was manually swapping a driver coil and setting taps on two tank coils when I moved the Collins 30o-G between 40 and 80 meters. I had that down to the same sort of 15 minutes, not including pushing the 1100 lb transmitter cabinet back and forth.
  4. N2DTS

    N2DTS Ham Member QRZ Page

    You just need enough transmitters to park them on the bands and spots you want.
  5. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Back before I re-activated the 8005 rig and acquired the Gates BC xmtr for 160, my only working transmitter was the HF-300 rig, so I had to do a complete change-over operation whenever switching bands. It uses five plug-in coils and the circuits all have to be tuned to resonance. Plus the antenna switching procedure which includes a trip down to the tower and back. I eventually had the procedure down pat, and I remember once timing myself for a complete band change from 75m to 40m in a little over two minutes. That was back when I was able to sprint down to the tower, which I can no longer comfortably do.

    Band changing is a little easier, now that a transmitter is parked permanently on each of the bands, on a frequency that I operate regularly. Just a couple of switching operations in the shack, band-switch the VFO and receiver, plus the trek down to the tower and back. The remote tuned circuits at the tower are controlled from the shack via a reversible DC motor and a series of mechanical drives. I rarely try to rush the job, just relax and go through the procedure step at a time. Usually takes about 5 minutes. Even if I had one of those frequency-agile plastic radios, I would still have to go to the tower to switch antenna configurations. I could possibly remotely switch antennas/tuners from the shack with a stepper motor, but with all the mico-electronics involved and the 140-ft control line, I'm afraid it wouldn't last more than a couple of months at this location due to lightning surges, even though I rarely if ever get direct hits.

    I do sometimes miss out on activity on one of the bands simply because I'm set up on another and lack the motivation to make the necessary changes to QSY.
  6. N2DTS

    N2DTS Ham Member QRZ Page

    Heard you on with Tim yesterday, nice signal into NJ.
    I have not heard you on for a while.

    Those plug in coil rigs were a lot of fun to band change, rigs like the old GK400 and other push pull link coupled rigs and exciters
    were a chore.

    You were talking about a gates stay level, was that like the old AM864?
    I duplicated one of those, 6SK7 tubes into a 6SN7 with a 6SQ7 doing the gain control.
    A simple circuit that seems to work well....
  7. W3SLK

    W3SLK Ham Member QRZ Page

    My MK-214D has 'shove-yank' 813's in it. To band switch you have to change the coil and add extra capacitance as needed. The oscillator and the the driver are 807's and can be changed with a band switch for each prospective section.
  8. KA4KOE

    KA4KOE Ham Member QRZ Page

    Don, it would be great if you shared the design of your remote tuning setup in the doghouse.
  9. K5UJ

    K5UJ Ham Member QRZ Page

    Does Cn not have to be adjusted?
  10. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page


    In both my homebrew rigs Cn (two of them, one for each tube) hold for all the bands I have coils for. The push-pull final is inherently balanced regardless. Single-ended with balanced plate tank coil, as in the BC-610 will hold neutralisation well if the circuit is carefully configured. Single-ended with balanced grid coil, as in the Gates BC1 series is a bit more tricky; it has been done but it's not easy.

    Simple. A separate tuner for each band / antenna combination. A large 5-gang ceramic rotary switch directs the signal from the shack to the proper tuner, and selects that tuner to feed the proper antenna. Each tuner is designed to have only one variable element, a variable capacitor that resonates the main coil. The five variable capacitors in the tuners are ganged together using ceramic insulated shaft couplings, a couple of 90° drives, a worm drive and reversible DC motor.

    The variable capacitors are adjusted remotely from the shack, but I have to go to the tower to rotate the big switch to change bands, or in the case of 160m, to switch between the vertical and dipole.

    Originally, before building the current dog-house, even touching up the tuning required a trip to the tower.

    Click on images to enlarge.

    Old Dog-house
    front view old.JPG

    New Dog-house, side view
    side view.JPG

    Front view, doors open. Rotary switch control and tuner components visible.
    front view.JPG

    Selector Switch
    selector  switch.JPG

    Selector switch control dial
    selector switch.JPG

    Attached Files:

    Last edited: Oct 19, 2021
    AD5HR likes this.

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