[ardf] Transmitters and Fox Boxes...

[Kuon & Dale Hunt]

>    1.  Do you use bulkhead connectors for piercing the ammo can, or just
>RTV the coax in a hole, or something else?

    I put a standard chassis-mount BNC jack on top of the box.  On the
    back I have a pigtail with a BNC plug for the transmitter.
    Well, a couple may have the type of BNC that takes coax on
    the back, maybe in different sizes... whatever I can find.


>
>    2.  Do you use different connectors (e.g., BNC, SO-259) for the 2m and
>80m antennas?  Where do you have disconnects?


     My boxes only handle one band at a time (at the moment).  Both
     use the BNC jack.  My 80m matching networks also have a BNC
     jack on the case and I connect them with a jumper.

     I have one practice transmitter with the tuning network in
     the same case:  this is convenient for setting it up, but
     I can't use a watt meter or SWR meter to check performance.
     Having the coax link makes life much easier for maintenance.

>
>    3.  For 80m do you use coax or twinlead from the box to the antenna
>(e.g., SO-259 or binder posts).

    Coax jumper to the matching network, which has a pair of bolts
    and wing nuts sticking out to connect the wires.


>
>    4.  Do you have a way to measure and adjust SWR in the box, or do you do
>that at home and assume everything is the same at the transmitter site?

    Do it at home and forget about it in the field.  Certainly this
    works with the 2m dipoles, and well enough with the 80m wires
    as long as they are fairly straight.

    On 80m you can put a large mica compression trimmer (perhaps
    500 to 1000 pf or so?) in series with the antenna for fine
    adjustment in the field.  Instead of worrying about an SWR
    meter I'd just take an audio field strength meter and set
    it up a reasonable distance away.  You should be able to
    hear the pitch change as you adjust the antenna.  Also
    gives a good check that everything is working if you place
    it a standard distance from the antenna.


>    6.  Do you try to eliminate the ON7YD oscillator noise on 80m?  How?

    I had the same problem with the Kanga "OXO" transmitters I used
    in 1999.  The solution in that case was to key the oscillator
    along with the final.  With the ON7YD transmitters you can
    use the 2m PTT lead to a switching transistor so power is
    only applied to the transmitter during the "active minute".
    Then the regular keying lead keys the final.  The oscillator
    will be audible between morse characters, but not during
    the minutes when the transmitter is supposed to be off.
    That's good enough.

    My current favorite "Pippin" transmitters key the oscillator
    along with the final, so there is no problem.



>
>    7.  Have you had any trouble with RF on feedlines or power cables?  Do
>you use Ferrite or loops of the cable/coax (common-mode chokes)?

    It might be handy on the 2m, but I've never worried about it.


>
>   8.  Did you try to keep the CG underneath the handle?  It seems like you
>have to put the battery in the middle of the ammo can to make it balance
>right.

   Usually the battery is bottom center, or close to it.  The two
   Hamtronics transmitters are in a metal chassis that slips into
   the end of the case, with the controller mounted on a sheet of
   wood alone one side.  The battery goes on the bottom, held in
   by wooden spacers screwed to the plywood.  Sometimes I use a
   wedge of stiff foam to keep the battery from sliding from side
   to side.  Using an HT, it usually ends up at one end (if it
   is short enough) or laying horizontally over the battery.
   Some of the backup cases have a 2Ah battery on the bottom with
   a slab of styrofoam wedged in, then the HT laying on top of
   that.  A couple more chunks of foam wedged crosswise keep
   it from shifting around too much.

   Actually, no matter how you arrange the contents of the case,
   the CG will be below the handle when you pick it up.  It does that
   automatically!


>
>   9.  How do you select 80m or 2m or both?  Switches?  Solder?  Change
>plugs at the Controller?

    I use separate transmitters with common connectors for antenna,
    power, and controller (5-pin header).  I just unplug one
    transmitter board and connect up the other.

>
>   Today I went to three different stores looking for ammo cans.  (One place
>advertised 50cal boxes for $2.99.)  They were all out.  *sigh*  Well,
>Tomorrow is another day.


    Think I got my .30 cal boxes from a travelling tool show that
    comes through small towns around here every year or so.  They
    were about $3 each.  Although the ammo cans are convenient,
    there are other options.  I started with a paint can and/or a
    nylon drawstring bag, and have used Tupperware containers on
    occasion.  Check the local Dollar store for some bargins.
    I also saw some waterproof plastic containers (similar to a
    plastic ammo can) at a Home Depot.  Other possibilities are
    lunch boxes, plastic tool boxes, or a length of large-diameter
    plastic pipe with a cap on each end.  The whole package
    really doesn't need to be that big.  Carrying 5 ammo cans by
    the handles - even the skinny ones - is a chore.


        - Dale


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