antenna question

jim · Post by **jim** » Thu Mar 28, 2002 9:09 pm

Question 1:
What's everyone's opinion on lowband base antenna? I'm looking for something with more receive than the standard "trombone" ground plane, which is currently one of the antennas on our repeater. The antenna in use now is very old and it's just time to replace it and do a little better this time- especially since a radial fell off last month.

Second question:
I know that in the 70's and 80's, a popular thing for low split lowband was to trim the whip shorter on a "Big Stick" CB antenna for low power use. Does anyone still have the spec sheet laying around if they've ever done one of these. I just happen to have one of these laying around and want to throw it up at home for monitoring the input, but don't feel like cutting 1/2" at a time until it tunes!! If somebody has the cut-sheet, I'll use this one for home otherwise a mobile will be just fine for what I'm doing.
I know....do the math, you lazy SOB!!

EC-7 · Post by **EC-7** » Thu Mar 28, 2002 9:27 pm

The math calculations for antennas are as follows:

1/4 wave: divide "234" by the freq = length in feet (most mobile ant)
1/2 wave: divide "468" by the freq = length in feet

"Big Stick" and "Antron 99" are 1/2 wave CB antennas, but they can be easily cut. I like the "Antron 99" antenna better, because it has two tuning rings and can be set for a wide bandwidth.

I think both antennas are rated at 1500 watts too.
_________________
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<font size=-1>[ This Message was edited by: EC-7 on 2002-03-29 00:31 ]</font>

astronut · Post by **astronut** » Thu Mar 28, 2002 9:37 pm

Its not just the antenna! Coax is a big factor too. The antenna will be a waste if you lose all of your signal on the way up!! First what band are we talking about? 30Mhz 40Mhz? A ground plane of which you were talking about is 0db gain. What coax were you running before? And how much of it? If this is 30Mhz you could tune an Antron 99 up there. If its in the 40Mhz you could use some of the 6m antennas down there. I really need a more precise frequency. I would recommend 9913 coax which has about 1db of loss at 30Mhz. Post the frequency and I will let you know which are some good antennas. Good luck

<font size=-1>[ This Message was edited by: astronut on 2002-03-29 00:40 ]</font>

Tom in D.C. · Post by **Tom in D.C.** » Fri Mar 29, 2002 4:37 am

Jim, You probably know this already, but when and if you start cutting the vertical to the frequency be sure to cut it several inches LONGER than the formula says so you can trim it to size.

Tom, W2NJS
...in D.C.

Jim202 · Post by **Jim202** » Fri Mar 29, 2002 10:48 am

In the past I have had good luck with the folded dipole style antennas on the tower. The DB-322 is ok if you don't have an ice problem. When the ice builds up on those, the SWR goes through the roof.

I think that Celwave use to make a good folded dipole that works better with ice. Don't have the catalog from RFS to look it up. Not sure it is still available. The paging companies loved them for low band.

Jim

jim · Post by **jim** » Fri Mar 29, 2002 2:31 pm

The frequency is 33.100

I already calculated the 1/4 wave stub on the Bigstick- assuming there isn't any tuning network in these antennas. As I remember from using them on 10 meters, they are just a piece of RG58 running from the coax connector up to the 1/4 wave rod. Not hoigh tech, but they do work.

We're currently using RG213 on the receiver. Although not the best, it's much better than what the original installer used (RG58!!).

HAs anyone tuned the Antron up this high? I've never tried it, but these cheap antennas actually work really well on many clubs' 10 meter repeaters.

What's your input, Will?

Will · Post by **Will** » Fri Mar 29, 2002 3:12 pm

I would try to cut the Antron or other CB antenna a little at a time testing with a low power signal. We used a end feed 1/2 wave on the 31 to 33 bands, High Gain made them in a commercial heavy duty dynamite proof antenna.
(1970s). The Ringos suck on LB. I used an Antenex VG302 on the last LB job, it was hard to get the correct tuning point, but comes with a cutting chart, and is reasonably priced. It is a end feed, shunt matched, one half wave lenth. Also check ComProd, in Canada, they are making the low band mobile antennas for my customers.(contact USSPS for details on ComProd)

jim · Post by **jim** » Fri Mar 29, 2002 8:51 pm

I heard this about the Antenex "ringos."

I'll try the Bigstick or Antron and see how it works. As most lowband antennas are unity gain, I don't really expect to see any advantage that any one of them would have over the others. We'll see what happens with one of these and some good cable and perhaps an RX preamp.

astronut · Post by **astronut** » Sat Mar 30, 2002 7:10 pm

At 33Mhz you should have no problem with the Antron 99. It goes up to 30Mhz. You will tune the tuning rings to the top. Second the top element is made to be cut. And you can purchase extras in case of a mistake. Do not use a preamp. It will make the repeater open to intermod and it raises the noise floor. the A99 has 3 dbi of gain. Remember to use brand new coax. Replace the old stuff and use quality. Not Radio Shack!! Unless you need every ounce of gain I would not bother to cut the top. I have had great success with the A99 for 11 and 10 meter. Good luck

jim · Post by **jim** » Sat Mar 30, 2002 9:39 pm

Radio Shack coax is good for only one thing- wrapping it around the neck of their employees that think that they know more than us and strangling them!
It has RG213 on it now, but I have a section of used (good) 7/8" hardline going on it.

Julian · Post by **Julian** » Sat Mar 30, 2002 10:04 pm

Ha ha! The employees there specialize in cell phones. I don't remember a time in which I went to RadioShack and WASN'T offered some great deal on a Verizon cell service. They're worse than the Military recruiters at the local job fairs!

Post by **HumHead** » Sat Mar 30, 2002 10:15 pm

I don't remeber why I was in Rat Shack buying $300 worth of stuff once, but I was, and actually had an employee who, after I asked why he thought I needed another cell phone (considering the cell phone, Nextel, and portable already on my belt), was honest enough to admit that a cell sale was worth more in commission than the $300+ of merchandise that I was about to ring up.

Bob · Post by **Bob** » Sat Mar 30, 2002 11:29 pm

I walked into a Radio Shack tonight with my VHF MT2000 on my belt. I got my parts and cashed out. On my way out the door, the kid saw the radio on my belt, looked at me and said "Is that a cell phone?" Mind you, the Sheriff's channel had been squalking for the last five minutes. It took a great deal of restraint to keep from ripping it off my belt, smackiing him upside the head with it, and asking "Does it feel like a cell phone?"

jim · Post by **jim** » Sun Mar 31, 2002 7:55 am

I'll have to walk in with my old MT500 lowbander clipped onto my belt and wait for them to ask "is that a cell phone?" just so I can do a 180 swing and wap 'em upside the head with the rubber ducky! "Does THAT feel like a cellphone antenna?"

That would leave a mark....for about 3 months.

These clowns at Crap Shack once tried to accuse me of stealing a cellphone case because mine was the same model as what they happen to sell. How I wish I had that old MT500 on that very day.

astronut · Post by **astronut** » Sun Mar 31, 2002 8:39 pm

Hey I worked at Radio Shack. And I am an amateur radio operator. Yes RS does sell junk. And I never pushed for Verizon! I pushed Sprint PCS he he!! We made 15$ off every cell phone we sold. Even more when you sold an accessory. Its not enough that you buy the cellphone we had to jam everything down their throat. The old people were the worst. Damn hearing aid batteries. Oh and the cordless phone batteries too!