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Author Topic: New station for a new ham  (Read 431 times)
RISER
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Posts: 2




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« on: July 05, 2004, 10:38:40 AM »

Greetings, I just passed the technician test, and had a question about a basic station I would to put together. I live in a condo so there are plenty of antenna restrictions, however I have access to my attic which is about 5 feet tall from floor to peak. I am thinking of setting up a base station using a mobile Yaesu 7800R with a Astron linear RS-20M to power the unit, I have a radio shack magnet mounted antenna (Catalog #: 20-032) placed on top of a large cookie sheet currently in the attic connected to my scanner. I hear plenty of 2m/70cm traffic on it daily. It says it can work up to 25 Watts of transmitting power on 2m and 70cm. It has a BNC type connector so I would need to get a simple BNC to PL259 adapter to connect it to the Yaesu 7800. I was wondering if this setup would work or if I need any different/additional equipment for 2m/70cm operation such as a SWR meter. I'm working on a fairly tight budget so thats why I'm choosing a mobile unit instead of a all in one base.(Setup: Yaesu 7800R to Astron RS-20m power supply to Radio Shack mag antenna) Thank You
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K1CJS
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Posts: 6055




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« Reply #1 on: July 05, 2004, 11:12:54 AM »

First, welcome to the hobby.  I think you'll find you can have a lot of fun with just your two meter rig.

To answer your question, your rig and power supply seem to be OK, but I would worry about your antenna.  Keep it for your scanner and put together a j-pole antenna for your rig.  That'll handle the power from your rig with ease, where you may be taking a chance using the Rat Shack antenna.

To get the plans for a j-pole, just do a search for '2 meter j-pole' on the internet.  You'll find a lot of plans for different types of j-poles there.

Again, welcome to the hobby, and good luck!
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N8UZE
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Posts: 1524




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« Reply #2 on: July 05, 2004, 11:16:48 AM »

Should work OK.  I tested a similar setup for a base station for my daughter (mobile radio, mobile antenna, cookie sheet for ground plane).  It worked great with no problems.  However, you should try to get an SWR meter.  They are not expensive and help you determine if your antenna is OK.  Some antennas are designed to be adjusted and you can use this to get the length correct.  An antenna analyzer would be even better but they are much more expense.  The SWR meter will let you know if you have a reasonable antenna setup.
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RISER
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Posts: 2




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« Reply #3 on: July 05, 2004, 11:35:59 AM »

Thanks for the replies! Looking into the J-pole now. I was wondering if you could recommend a decent 2m/70cm SWR meter? The MFJ's in eham's review section dont seem to be getting good ratings.
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K0RFD
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Posts: 1368




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« Reply #4 on: July 05, 2004, 01:17:14 PM »

A J-pole is probably going to be a good way to go.

I just measured a roll-up J-pole that I made out of 300-ohm twinlead to keep in the glove compartment for emergencies, and it's 58" from top to bottom including the matching stub.  If you have 60" height in the attic, a twin-lead j-pole might be a good way to go because its flexibility might make it a little easier to install than the "copper cactus" variety.  You can hang it from a rafter with a short piece of string.  Because it isn't going to be out in the weather, no need to go the copper pipe route.  It will work just about as well.  You can build and tune one in less than an hour, and if you want some plans I can email them to you.  Just make sure you run enough feedline into the attic to leave enough extra for 4-5 wraps about 4" across to use as a coax choke balun.  J-poles like to be fed with choke baluns.

If you can't find enough inches of clear space, you can build a simple 1/4 wave ground plane out of some bronze welding wire and an SO-239 connector.  Plans are in the ARRL antenna book and/or at the ARRL web site.  These will work well with your rig also, not as much gain as the J-pole but much better than your magmount and a cookie sheet.

Regarding the VHF/UHF SWR meter, I'd strongly advise borrowing one from a local Ham for the brief length of time you'll need it to build and tune your antenna.  I've had one for years and that's the only time I ever used it.  It's not something you're going to use very often and if you can meet some other Hams in the area you probably don't need to buy one.  Once your antenna is built and tuned, the SWR probably isn't going to change unless something drastic and unfortunate happens.
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W4TYU
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Posts: 518




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« Reply #5 on: July 05, 2004, 02:53:09 PM »

What length feed line will you have? And what kind is it? When measuring SWR it is best to position the meter at the antenna since the attunation or loss works on both the reverse signal and the forward signal.

The antenna setup you now have will work nicely for transmitting as long as you do not exceed the power limits of the antenna.  Depending on your location to the repeaters a J-pole may or may not give better results. If reception of a signal is marginal on your present antenna then the J-pole will probably help.

At any rate, a J-pole is fun to make and a learning experience.

Ole man JEAN
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N6AJR
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Posts: 9921




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« Reply #6 on: July 05, 2004, 03:28:14 PM »

I had a friend who put the mag mount on his refridgeator and he couldn't hit anything, but we mofed it 2 feet to the right and a couple feet lower, and put it on the stove and he got into every local repeater.  

I don't know if it was  a better ground plane, or a different angle, or what. point is to move it around untill it works well.

you can also make a ground plane antenna with a so239 connector and 5 pieces of 19 1/2 wires , solder 1 to the top and 4 at 45 degrees on the 4 holes in the connector. do a google on 2 meter ground plane, or home brew 2 meter antenna etc.  they work well..

 welcome to the gang and have fun.  remember there is more to life than 2 meter fm repeaters...
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KZ1X
Member

Posts: 3229




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« Reply #7 on: July 05, 2004, 08:29:36 PM »

... if you are going to stay with your mag-mount idea, consider getting an Austin 500C dual-band mobile antenna and the Radiall-Larsen NMO-MM mount.  HRO and others sell them both.

This is not an expensive antenna, but it's an investment nonetheless beacuse you will never get rid of it.  A dual-band FM magmount is always needed, and you will own this antenna for all the years that you will be a ham.  Fads come and go, but quality stays.  

Oh, and the Austin is very low-profile, too.  Great for sticking on top of the fridge!

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