John,
The lynchpin to having a good signal when operating low power portable, is a
good antenna.
Some people take a great rig, run it at reduced power on a crappy antenna
(i.e., mobil whip mounted to a ground stake), and wonder why they don't work
anybody.
Wire can be a wonderful antenna, but you have to get it up high in the air.
That's why I always took a telescoping fiberglass pole with me.
In the early days they were just 8m long.
Later there were some purpose-built poles for ham radio that were 10m long.
Today you can get them in even stronger quality in lengths of 12m or 18m.
In fact they even come as long as 26m but that's a bit overkill for a
one-man expedition.
For Field Day I always ran a doublet, with each leg 13m long, and fed with
300 Ohm Openwire.
I had a tiny little MFJ Matchbox (T-filter), with a built in Balun.
The Balun was great for 5w QRP or 20w, etc., but I burned it up running
100w.
Had to re-build it, then never tried 100w with it again.
For my normal excursions I had a special lightweight 3-band dipole:
- made of thin Teflon-insulated stranded copper wire (I guess about AWG 22
or so)
- cut for 20m, insulator, more wire for 40m
- 2x short jumpers for jumping the insulator between 20m and 40m segments,
for 40m operation
- 2x short stubs with alligator clips to extend the antenna for 15m
operation (6 inches on each end)
- fed with about 50' of RG-174 (YES, THE THIN STUFF).
- A ball of twine for tying off the ends
Twine was cheap and disposable if it got too tangled. Ends tied off to
trees, or if nothing else, simply to stakes in the ground.
The thin RG-174 is sufficient and loss is really not bad for short runs at
those frequencies. The loss is worse if you use heavier coax, and then fail
to get the antenna high in the air!
A 40m dipole has a fairly good match on 15m but unfortunately on the very
high end of the band.
What you want to do is cut your dipole for about 7.1 MHz.
Then when you use it on 15m, clip about 15cm (6") of wire on to each end (I
used alligator clips), and just let the stub hang. This drops the 40m
resonance near the bottom of the band, which moves the 15m resonance to a
more usable spot.
The key is to get the center (point of max current) as high as possible.
Therefore the fiberglass pole.
But you can't hang a lot of weight on the pole, so you can't use a Buxcom
Windom or a Morgain dipole.
You have to design a lightweight dipole from the ground up.
Notice: NO BALUN. By low power and portable field operations, what for?
If you think you MUST use a balun, then about a foot before the coax would
reach the ground, wrap about 8 to 10 turns of the coax around a 3" piece of
PVC pipe. Then when erecting the antenna, slip this over the pole; that
will hold it in place.
This was my primary antenna for most operations (except contests).
Source of good quality fiberglass poles: W4PA, (Scott)
73
Rick, DJ0IP
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of John
Sent: Wednesday, March 28, 2012 12:42 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Using an Argosy in the field
Rick,
Thanks for your comments and estimates. It always helps if estimates are
based on reality. I was thinking of trying SSB but was really unsure of how
I would get out on sideband. The group I do FD with generally will have at
least one run for QRP contacts for their point value. If things quiet down,
I could insert the Argosy and still have access to the beams although with a
little thought I could also use whatever I wanted. I will now have to go
and look at the rules for low power operation.
I have made a few low power contacts and 50 W contacts with the Argosy on my
antenna here at home so it is not like I have never tried it.
John / WA1JG
On 3/27/2012 4:46 PM, Rick - DJ0IP / NJ0IP wrote:
> Steve, you are way off on your assumptions.
>
> Normally the TX current drain is not the biggest problem.
> Continuous current drain is the problem.
> I would say you will be on receive 90% of the time.
> When talking you probably average only 30% of max current drain.
> On transmitting CW it might be 50%, probably less.
> But as I said, 90% of the time that the radio is switched on, it will
> be in RX mode.
>
> Important is continuous current drain:
> - Turn off the dial lamps (can't remember if there is a switch on
> that rig or not; if not, install one)
> - Use headphones instead of speaker; that way it draws less current
> - Turn the radio off every chance you get (breaks for eating, etc.)
> - If it gets dark, use an external LED lamp to light the rig's front
> panel (I used to use candles)
>
> Run as little TX power as necessary.
> For CW, 20w is generally enough (if you feel you have to run more than 5).
> Running in QRP mode saves more than you think because it is more
> efficient in that mode than when running reduced power in high power
> mode. What I mean is, if you switch it to QRP, it draws perhaps 800mw
> on TX. If you run it in high power but back the power off to , say,
> 10w, it doesn't draw twice the current, but rather 3 or 4 times as much
current.
>
> I hope your Argosy is the analog version.
> It will draw less power in receive than the digital readout version.
> You will find that the dial lamps draw half of the total current in RX
mode.
>
> My Experience: 18 years of running Ten-Tec transceivers from a
> motorcycle battery. Transceivers used: Ten-Tec 505, 509, (both with
> and without the
> 405 amp), Ten-Tec Argosy (analog), Ten-Tec Scout, and Argonaut 515.
> You can see some photos of my setup here:
> http://www.dj0ip.de/my-expeditions/
> SPECIFICALLY, check out the ones to the Isle of Man, and Corsica.
>
> ALSO, check out my 1979 operations from Andorra.
> I ran a Ten-Tec Omni (analog, dial lights switched off, running @ 50w
> CW) for 10 days off of car batteries.
> Generally one car battery would last me an entire day, and I was on
> the air about 16 hours per day.
> I could recharge the battery on our generator which was located near
> the SSB tent, about 200 meters away from the CW tent.
> I felt like I was transmitting all the time (or so it seems when
> you're doing it), but the reality is, you receive far more than you
transmit.
> See: http://www.dj0ip.de/my-expeditions/andorra-1979/
> In my 1975 expedition to Andorra, we also ran off of the car battery
> (that's all we had) but we ran the car's motor quite a lot, just to
> keep warm. We ran an old Swan SS-100 (well it was brand new then) with
50w out.
>
> RUNNING FROM THE CIGERETTE LIGHTER:
> It's not a problem to run the full 50w off of the car's cigarette lighter.
> You need to purchase a special device for this.
> Check out the MFJ-4403 transceiver Voltage Conditioner:
> http://www.mfjenterprises.com/Product.php?productid=MFJ-4403
> It works.
>
> VERY IMPORTANT: ALWAYS HAVE JUMPER CABLES WITH YOU WHEN RUNNING OFF
> OF YOUR CAR BATTERY.
> You can almost always find another driver/car willing to jump start
> your car, but they don't always have jumper cables.
>
> Have fun!
>
> Rick, DJ0IP
>
>
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