PRO-97 and external antennas

[KE7TJK]

I'm running my PRO-97 in my vehicle, and have been using a Larsen NMO-150 5/8 wave external antenna, with 3db gain.

I have noticed when using this antenna that the scanner seems to overload in some areas, and reception in one part of town is almost non existent, or it is very scratchy and distant sounding. All of the freqs I listen to on 150 are on repeaters atop either the surrounding hills, or on the tall buildings downtown. In this 'bad' part of town, I can switch to the rubber duckie, and instantly my reception improves to normal. I never had this problem using the same antenna on an older mobile scanner.

Today, I stopped in to the local radio shop, and picked up a Motorola NMO mount 1/4 wave, and replaced the Larsen. So far, on my side of town, it is working the same, if not a bit better than the 5/8 wave. Haven't been to the area that I have problems. I'll report on that later.

My question for you PRO 97 users is have you noticed overload on your scanner with an external antenna? If so, what have you done to mitigate the problem. I DO get some intermod with the 5/8 larsen, but not to where it covers anything up. With the new 1/4 wave, I have noticed no intermod as of yet.

I'd appreciate hearing your experiences.

 

[Grog]

A lot of the GRE scanners overload on VHF Hi. I've had it with the 93, 97, 2053, and I'm sure i will with the 2055. I try not to use a high gain antenna for local monorting anymore.....

 

[MacombMonitor]

Try enabling the Attenuator, that should solve the problem.

 

[KE7TJK]

Try enabling the Attenuator, that should solve the problem.

That did not work. It was the first thing I did.

I had the very same problem with my PRO-95, which was one of the reasons I sold it. Did the exact same thing as the 97.

As I stated, I used to have an old Uniden 16 channel mobile in my vehicle hooked to this antenna, and never had any such problems.

I also want to be clear; my problem is NOT intermod, or bleedover. It is bad reception in one part of town with the external antenna. Reception is fine when on the rubber duckie.

Another oddity with this setup is that the repeaters for local PD and fire is located less than a mile from me when at home, and this is the area that the mobile setup works the best. Across town is where that hi gain antenna seems to fail the 97.

I've got to head out across town to the area I've had the problems with tomorrow, and I'll report back on the performance with the 1/4 wave installed. I'll laso try my BR-330T and see if that does the same thing.

 

[MacombMonitor]

Do you have any FM broadcast stations in the area...or high powered paging transmitters? If so, they could be saturating the front end of the receiver and desensitizing them, as Radio Shack (GRE) scanners are as a rule, are more sensitive than Unidens.

If the answer is yes, then a filter may be needed. PAR makes some really good ones!

Click here:

http://www.grove-ent.com/filters.html

 

[MB]

I have the same problem when I use my PRO-97 at my house with an external antenna. However, when I activate the "Global ATT" or "ATG" this problem totally goes away.

When you say you tried the attenuator, did you mean the ATT per channel or the Global ATT?

I find that my GRE scanners overload much easier then my Unidens do. Also I find that my Uniden BC780 is first as far as sensitivity goes and then the BC898T is close behind. In general my Unidens seem more sensitive then my GREs. This may be because my GREs are slightly overloaded.

 

[KE7TJK]

I've tried the global ATT because the problem occurs on all freqs.

The area in question is at the foothill of a large ridge that has all of the T.V. station and radio station transmitters on it, as well as near a local A.M. transmitter. The ridge also has a couple of public safety repeaters on it , and I only have intermittant prroblems with those freqs when in that area.

I didn't get a chance to use the scanner in that area today; drove my wifes vehicle instead. (Mini van; she made me do it. )

Thanks for all of the suggestions. I'll report back when I have my rig in that area.