ARRL

Marksail2

Joined: Mon, Apr 8th 2013, 00:09 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
Grab-and-Go, pwr for Satalitte and ECOM use Jul 10th 2013, 00:00 3 826 on 13/7/13
Antanna Tuners Jun 24th 2013, 20:55 3 774 on 25/6/13

Latest Posts

Topic Author Posted On
Grab-and-Go, pwr for Satalitte and ECOM use Marksail2 on 10/7/13
BY physical limitations (as a human) I have taken older radio gear / equiptment and putting them to use in alterantive ways. I HAVE a Yeasu FT-7100 Dual Bander in my truck that is now is re-mounted into a 'grab-and-go" suitcase. I started my 'Project' by providing power with a 5 cell 12VDC battery pack rated at 4.5 amp/hrs. Basic electricity tells me that in a fully CHARGED case I couldn't and wouldn't want to draw more than about 4 Amps! (that is assuming a 3-4 amp dead key, and 100mA listening - on LOW power. with the radio) Given a 80% listening / 20% transmit ratio lies well within a 2 hour operating limit. What I am finding in practice is even a 'dead key' without modulation will kill the voltage and lead to a garbled transmission. My first assumtion is to add an additional 'pack' rated at 4.5 A/h in parellel with the first to increase not only amp draw, but battery life as well. While these small NiMH battery packs work well for remote airplanes and the like, they seem unsuitable for High draw applications. Seems (in my mind) that it would be best to leave the "grab-and-go" package intact - ie: small batteries for set-up, recieving, then port out the MAIN power cableing to either a cig plug (or powerpole connector) to something like a Marine U1 battery that could susstain amp draw over a longer period and still accept an amperage peak while keyed. It seems I am throwing my money at a problem (small battery packs) while what I should be doing is investing in a HIGH A/hr, marine battery! Once that is done, my electrical curcuits become a little more complex as I know from experience, marine 'type' batteries discharge explosive gases and are also prown to overheating from re-charging. I am also a sailboat owner and KNOW if you re-charge or even discharge (rapidly) even Gel-cells, you create an extreemly volitile environment, with cells reaching max. temp in a hurry and in combination with dicharge gases, try and light a cigarette! BOOM!
Anyone who (in my opinion) builds a battery pack without temp and /or gas monitoring is asking for trouble! Ask to see my scars from an airplane battery explosion on a business class jet while working as an aircraft mech.

The point in all of this dribble is I am asking for help in putting together a design for my FT (Yeasu) that is safe portable and reliable without a major cost of construction.

My ultimate goal is to use the FT as a satellite tracker / EMCOM station IN THE FIELD. While sat passes rarely last more than 10 minutes, sustained operations is not a must, but would also go hand-in-hand with EMCOM.

Hope for some help and advice as I KNOW we have many very talented people out there!

KK4RVL,

Mark
Antanna Tuners Marksail2 on 24/6/13
I am a relatively new ham and have a general question.

Operating my Kenwood TS-2000, but not limited to this radio...It contains an internal antenna tuner. This radio as well as after market stand-alone tuners fit into the same catagory, ie: they don't tune in any band except HF. Like 2m for example. I am operating an antenna with a loading coil at the base. Band selection is done by selecting a 'coil' to short the coil and varying the length of the 'conterpoise' wire. On 2m I generally know I am tuned by watching an external SWR / Watt meter. With this method I can usually get in the range of 1.5 to 1. Once the radio is tuned to a HF frequency I use the manufacter's recommenadtions for whip, conterpoise length and coil for each band, then 'automaticlly' tune the antenna for optimum SWR etc.

My question... why are they NOT antenna tuners for bands above HF? I am assumig electrically they are possiable, but maybe not practical from a design stand point.

Tx,

Mark, KK4RVL

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