want to extend range

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skunkhaze

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Hi everyone, i have a Diamond D130J discone. I'm up in North County near Oceanside. I can listen to the county RCS fine, I'm trying to pull in the City of San Diego im about 40 miles away from the city. I was wondering what can i do to try to extend my coverage? I was thinking of installing a preamp and a filter.

or maybe repositioning my discone, there are a couple of trees and power lines in the area which are of normal residential load im not sure how much this effects reception.

I'm running RG8 coax straight from the discone to a BNC to the scanner, i was wondering what adapters i could use from RG8>bnc for the preamp. These are the preamps and filters i was thinking of using:

WRP-2500 Pre-Amplifier for Wideband Scanners

http://www.scannermaster.com/ATT_20_Variable_Attenuator_p/24-531021.htm

I'm worried about overloading my scanner on the county RCS but i think it has a bypass and power switch so i could avoid this issue.

Please let me know what your thoughts are.
 
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W6KRU

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I live across the freeway from the harbor in Oside. I hear all three RCS zones and the city just fine. i suggest a better antenna rather than a preamp. You can see the antennas that I use listed in my sig. The yagi is overkill and I don't hook it up very often. The ants. are only 10' off the ground allowing me to use very short runs of RG6. If you research those antennas they are pretty pricey but I just watched Ebay until I spotted a deal They are for the cellular freqs.which have very low demand these days and I got them for less than $25 each delivered. Since those antennas are designed for ~ 850 MHz, they are sort of like having an inline filter but more efficient. I can't even hear broadcast FM using them and I think that is part of the reason they work so well for 850meg. Good luck.
 

skunkhaze

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How funny im near Coast highway and the bridge going into the Habor. interesting suggestions you listed
 

Ben96cal

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re: better setup

Ditch the preamp idea on 800. Will blow out front end.. change out the RG8 for 9913F and get an antenex 800 yagi and point it the direction you want. works like a charm. I pick up trunk systems 90 miles away.
 

avtarsingh

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i wouldnt go with 9913

i would use lmr400 or 1/2 in hardline ..

but the rest of what ben says is really good

i dont like 9913 because of the water migration problems it has
 

Ben96cal

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re: setup

i wouldnt go with 9913

i would use lmr400 or 1/2 in hardline ..

but the rest of what ben says is really good

i dont like 9913 because of the water migration problems it has
9913F is flexible, good grade and has the same loss characteristics of LMR400 at half the price..
 

bryan_herbert

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I agree with LMR400. I live 30 miles North of Downtown Los Angeles in Newhall and used to run a discone 20 feet in the air and could pull in OCFA with no problem. It survives the harshest environments and lasts for years plus you can find it in bulk on ebay or at online surplus stores fairly cheap.
 

gewecke

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I too have to second using LMR 400 as a better grade of cable,and at least a 6 element yagi like a cushcraft or a DB products. I would however stay away from using a preamp.
n9zas
 

trooperdude

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First, discones absolutely SUCK at 800 mhz. Especially Ham discones.

By adding a cheap pre-amp you would only amplify the noise.

Get a quality 800mhz yagi and LMR400 or ( Preferably) LDF flexible hardline.
Don't waste money on 9913F or RG6 satellite coax.

Point it in the correct direction of the transmitter you want to listen to. Try not to use adapters at 800mhz, as you lose at least 3 db of signal with each adapter.

There are deals on fleabay for antennas and cable. You just have to look around.

I don't think I paid over $20 for any of my 800 yagis and all were new in box.

I picked up a couple of 800 Antennex Omni's for about $40 each, if you have multiple sites in differing directions to listen to, that is
another option..

But bottom line is dump the discone for anything UHF and above. Band specific antennas and quality feed line are always
better.
 
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skunkhaze

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Hmmmm, I initially bought the discone as i started out in this hobby, So far it has satisfied my needs. I'm using about 50ft of RG8. The reception is great i can pick up Air Traffic and Military air easily thats one of the great things of the discone is used for that. I do noticed like ya'll are saying about the 800 mhz before the firmware update it was was horrible, now i can adjust the P25 response time. And before it was always incomplete transmissions or just unstable. Now its fine my County RCS comes in loud and CLEAR which is a MOT2 Trunk system P25. But whats strange is that i could take my 246T about 3-4 miles down and find the repeater for the City of San Diego, but my discone cannot hear that system at all. So before i invest in another antenna i may just try reposting the discone and see if that helps. as Far as cable goes LM400
 

jim202

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Can I ask where your getting your info on adapters being this lossy?

I have been in the radio engineering field for over 45 years now and have never seen anything published
that comes even close to this number. Maybe 0.3 db loss is more like it. The exact number depends
on what frequency your trying to use the adapters at.

Jim




Try not to use adapters at 800mhz, as you lose at least 3 db of signal with each adapter.
 

trooperdude

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Can I ask where your getting your info on adapters being this lossy?
Anritsu site analyzer, and almost every modern ADAPTER I've run across lately in
systems..

The exact number depends
on what frequency your trying to use the adapters at.
Figure quoted was average, but NO WHERE near as good as 0.3 db
Loss of course is much less at 42 mhz than 800 mhz

YMMV, but it's still my opinion that adapters SUCK.

BTW the discone mentioned, with RG8 at 800 mhz, is basically acting as a dummy load, but better than wet string.

If the poster is married to the Discone, at least change out the coax.
 
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zz0468

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I have been in the radio engineering field for over 45 years now and have never seen anything published that comes even close to this number. Maybe 0.3 db loss is more like it. The exact number depends on what frequency your trying to use the adapters at.
I did some experiments a while ago, and measured a bunch of adapters on an Agilent Network Analyzer. In all the various combinations, and quality ranging from cheap radio shack adapters, to high quality gold plated adapters, in no case did I ever measure more than 0.1 db loss below 1 GHz.

The difference in quality shows up in the microwave region.
 

zz0468

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Anritsu site analyzer, and almost every modern ADAPTER I've run across lately in
systems..
That 3 db figure is extremely high. Are you sure your measurements were done with a properly calibrated instrument? There are plenty of places in the measurement process that one can be fooled, unless you're really careful.

As I stated in my previous post, I did some experiments with a large batch of adapters - UHF, BNC, N, SMA, RCA, F, and various combinations. Some were very high quality, and many were bottom of the barrel radio shack components purchased just to test. In all cases, under 1 GHz, the loss was insignificant. This was done with an instrument and test cables calibrated, and verified with lab quality standard references.

I suspect that the biggest problem in using adapters is not the adapter itself, but in a poor quality installation of the connector attached to the adapter. In carefully tested lab quality test cables, the adapters themselves are not the problem, below 1 GHz. Above that, all bets are off.
 

SkipSanders

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I would suggest one thing you should pretty much always do when you put up an outside antenna in an urban environment, especially a discone, is put an FM Broadcast Band trap in the line.

It is very, very often the case that strong FM broadcast signals will desense your front end on a scanner, most of which were NOT designed for outside antennas and 'expect' the signal levels from a back-of-set antenna.

One possible filter is: HPN-30118 Combined Notch Filter

It will cause some loss in the VHF Aircraft band, though.
 

avtarsingh

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you guys are getting hung up on the loss issue of adaptors and leaving out 50% of the reasons why you dont use them

they fail
it's 1 more thing to break or fail and creates a bigger path for water migration


i dont like adaptors because its so easy to use the correct adaptor and it just shows laziness on the tech

you already have a soft jumper on both ends (or should have ) do you really need more adaptors and more paths for water migration ?

the fm trap is a great idea ..i have several types and i usually put it near the scanner itself

many scanners get hosed really bad by fm i have a big fm xmtr near me and without the trap inline i cant hear 72.46 at all i put the trap inline and instant full scale readings return for chp
 
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zz0468

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you guys are getting hung up on the loss issue of adaptors and leaving out 50% of the reasons why you dont use them
I'm just trying to dispel the myth that they have this humongous amount of loss. Used correctly, they don't.

they fail
it's 1 more thing to break or fail and creates a bigger path for water migration
Cheap ones do. But this is a good point, particularly about water entry. Any time the coax jacket is broken, that becomes a possibility.


i dont like adaptors because its so easy to use the correct adaptor and it just shows laziness on the tech
In many cases, this is true. But not always. In the case of a stiff heavy cable interfacing to an antenna or a radio, a lighter, more flexible jumper is required. Sometimes best practices dictate that an adapter of some sort be used. So, one just uses them, and doesn't worry about the loss.
 
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