[ADXA] Advice for Mobile Operations

Fri Oct 30 15:32:29 EDT 2020

Hi Trent,

If it were me I would go straight from the radio to the Battery first with both + and – leads.  However, on some new models this can be problematic?  In the days before computerization, this method was the first thing what was recommended for a mobile installation.  In today’s newer models, some computers may think the extra wires at the battery as some sort of fault within the system.  Totally electric vehicles are very different beast these days.  So you have to check with the manufacturer first, but that info could also be on some websites?  

Yes bond the Radio to the body/frame, but only after you run the power supply cable direct to the battery or recommended source provided by the manufacturer.  If the manufacturer says direct hookup to the battery is not a good way for your particular model, they will tell you were to hook up the power leads properly or should.  Do not use just the minus lead hooked to the body as the only method of ground return, that could act like a fuseable link and toast your radio or worse cause a fire!  

At the back of the tail pipe put a good bond there to the frame.  Many resources using tinned copper braid or large copper wire to do your bonding with.   That will help on the noise as well.

When you go to 40m and below, everything becomes much harder.  You need a good solid mount for the antenna and again, bond the antenna base right to the frame and chassis.  Do both and it will help with both the match and noise.  Mag mounts are not much use on the lower bands, IMHO.

Finally some series inductance may help you on 40m and 80m bands on getting a better match.  You can experiment with just a few turns of solid copper wire.  In the end working DX is fun from mobile and you can go to quiet locations, hi.

Rick Harris gave you the best website for mobile operation that I know of.  The ARRL could some info on their web site and in their Amateur Handbook that is also worth a look for proper mobile operation.  

Good luck on your installation!  Running mobile is hard work, but enjoyable after you get everything done correctly.  

FWIW, years ago FSAARC would do the ARRL SSB DX at WhiteRock.  One year I had to come home to attend my son’s basketball game, but managed to work 45 countries on the way home to Fort Smith.  Even at the in the valley surrounding Whiterock!  Logging was super hard as I had to pull over to complete the log, hi.  Working them was easy!  I spent more time working and logging, probably took me an extra hour to get home?  BTW,  I was using bug catcher on 40m with a 3 inch coil at the time and 100 watt rig.  The whole antenna was very long, about 12 feet or so on the back of a S10 and later I move that to a Tahoe.  It would whacked a ton of trees everywhere I went, but it worked great.  😊

73 de w5jay/jay..

From: adxa-bounces at mailman.qth.net <adxa-bounces at mailman.qth.net> On Behalf Of Trent Fleming
Sent: Friday, October 30, 2020 11:08 AM
To: adxa <ADXA at mailman.qth.net>
Subject: [ADXA] Advice for Mobile Operations

Good morning,

Slightly off-topic, but I do intend to work DX as much as possible from the vehicle.

I recently upgraded my FT-8900 to an 857D in my Tahoe.  I'm using a mag mount with a 40m ham stick. I have the radio in the back of the unit, with the separation kit using a Lido floor mount (which I'm very happy with, and actually used with my 8900 as well.

 Earlier this week I drove a big circle from Memphis to Columbus Ohio back through Southern Illinois and on to Memphis.  I was extremely pleased with the performance of this setup from a receiving standpoint.  Sunday afternoon I listened to several contest stations from Europe, South America and the Caribbean working stations in North America, Asia, etc. 40, 20, and 15 were all very readable.

Monday afternoon and evening, as well as Tuesday afternoon and evening, I listened to domestic stations on 80, 40, and 20.  I was able to listen in on the Arkansas Razorback net at 630pm both nights, hearing not only net control but many of the check ins.

At this point, in spite of my antenna analyzer showing a good match around 7.2 mhz, I am unable to transmit with any power due to high SWR.  I also have significant noise on 40 and 20 when accelerating, but very little noise at cruising speeds on any band, or while idling.

So, I have some work to do, but I have these questions for those of you who operate mobile HF

1) do you ground the radio to the car body?  If so, how?

2) what type of engine noise suppression, if any, have you used?

3) is the magnetic mount less than ideal?

4) I'm looking at the ATAS-120, versus the Tarheel antenna.  I think the tarheel, with a lip mount on the back lid of the Tahoe looks like a good idea.  I also see much better reviews on the Tarheel vs the ATAS-120

5) Thinking about trying my LDG remote tuner (which I used at the base of my 43' vertical antenna) on the hamstick to see how it does

Thank you for any and all suggestions - I am primarily interested in responses from those who have successfully implemented mobile HF.

Feel free to respond directly if you feel this is too far off topic for the list.

73,

Trent

N4DTF

EM55

-- 

Trent Fleming

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