Confused - rubber duck works, discone - no reception

OntFF221

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Hoping someone can help - I’m at my wits end.

I have a Uniden BC325P2 for monitoring local fire departments; and feeding into Broadcastify.

setup is a Diamond 130N about 30’ AGL - RG6 down to a grounding block, then into a splitter; feeds a GRE500 for EMS and police, that works perfectly.

other leg of the splitter feeds the Bearcat... it picks up analog fire (150 MHz ranges) great... but the regional system (770 MHz) doesn’t get picked up.

If I disconnect the antenna setup and use a rubber duck, I receive the regional system fine; so I know the programming is ok... but I can’t get the analog fire channels, as they are further away.

The antenna is wideband; and while I know RG6 isn’t ideal, for receive only it shouldn’t be a big deal...

I’m at a loss here - any suggestions?
 

iMONITOR

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Try removing the splitter and connecting the antenna to the BCD325P2 directly and alone.
 

OntFF221

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Monitor - thanks; sorry - should have mentioned I tried that; also tried adding a 3db attenuator, in case the scanner was overloading.

Great suggestion, and appreciate the idea!
 

KEWB-N1EXA

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Lack of signal or the opposite your Bearcat is over loaded !
Where I live I cant run pre amps because the local FM tower miles away which has 2 stations on it blows out the Bearcat 15X.
It sits there on some bands as a dead duck !
I have a Bearcat 785 that on the airband had FM radio in the back ground.

RG6 is fine for Scanner reception its 75 ohm and your not Transmitting on it !

Peter N1EXA
 

kruser

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It's possible the discone is picking up several towers if this is a simulcast system having issues. That very well could be causing bad LSM and the 325P2 simply can't decode the signal.
Do the analog fire channels that you mentioned come in okay with the discone?
 

iMONITOR

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Was this setup ever working at one point or are you trying something new? Discone's are not the best choice for 700-800MHz and they are zero gain. How old is your coax and how long is it. Did you use a lot of adapters or any splices along it's length? Any chance water get into any part of the antenna system? How far away is the 770MHz regional system?
 

iMONITOR

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Where I live I cant run pre amps because the local FM tower miles away which has 2 stations on it blows out the Bearcat 15X.
It sits there on some bands as a dead duck !
I have a Bearcat 785 that on the airband had FM radio in the back ground.

Peter N1EXA
Have you tried an FM-Notch filter? They work great for that type of interference.
 

KEWB-N1EXA

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Have you tried an FM-Notch filter? They work great for that type of interference.
I need to buy one and try it out.

Saw some on ebay that were pretty affordable.

I had an old Channel Master TV FM band pass filter that was pretty broad and did a job on the airband too. Wiped out 118.1 for the local tower !

In my case I just don't run Pre amps and seperate the 800mhz monitoring to one scanner and VHF monitoring on others.

Pete N1EXA
 

KEWB-N1EXA

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Was this setup ever working at one point or are you trying something new? Discone's are not the best choice for 700-800MHz and they are zero gain. How old is your coax and how long is it. Did you use a lot of adapters or any splices along it's length? Any chance water get into any part of the antenna system? How far away is the 770MHz regional system?
Agree here I find Discones are great for VHF airband/Marine/Rail and Military Air 250- 300 Mhz UHF but it rolls off for 850 Trunk and 950 DMR its awful !
 

Ubbe

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setup is a Diamond 130N ....... it picks up analog fire (150 MHz ranges) great... but the regional system (770 MHz) doesn’t get picked up.
Due to the direction lobe in a discone that tilts up in the sky at 700MHz and above, the signal are down by 10-20dB. But if the signal are at least 20dB stronger using the rubber ducky, a 100 times stronger, then it should be picked up by the discone, if the discone isn't too good and the scanner receives several sites from a simulcast system and the rubber ducky only sees one site thru the window.

Do you see a huge increase in signal strengt at 150MHz for the discone compared to the rubber ducky? If not then there's something wrong.

/Ubbe
 

OntFF221

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To answer the questions above, in no particular order:

- No, it's never worked properly.

- I do see a great improvement in strength on the 150 Mhz bands. With the rubber duck, I only get the local FD; the others are 15-40 km out; with the discone, they come in fine.

- CoAx is brand new. Soldered on N connector at antenna end, Snap-N-Seal style connector at splittler/scanner end, using an "F" to BNC adapter. About 35' long. No splices or anywhere for water ingress, solid piece from the antenna to the scanner.

- The 770 Mhz P2Ph2 system is simulcast. One tower is 3 km away to the SSW; other 2 are about 18-20 km. One tower is due East, one is North-West.
 

iMONITOR

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To answer the questions above, in no particular order:

- No, it's never worked properly.

- I do see a great improvement in strength on the 150 Mhz bands. With the rubber duck, I only get the local FD; the others are 15-40 km out; with the discone, they come in fine.

- CoAx is brand new. Soldered on N connector at antenna end, Snap-N-Seal style connector at splittler/scanner end, using an "F" to BNC adapter. About 35' long. No splices or anywhere for water ingress, solid piece from the antenna to the scanner.

- The 770 Mhz P2Ph2 system is simulcast. One tower is 3 km away to the SSW; other 2 are about 18-20 km. One tower is due East, one is North-West.
If by "splitter" you mean just a BNC or Type-F Y or T adapter that's likely your problem. You probably need a multicoupler, preferable a amplified one, like this:

1605628678290.png
Stridsberg MCA204M
VHF/UHF Receiver Multicoupler - 25 MHz to 1 GHz - 4-ports
 

gmclam

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I am using a discone and am very happy with my reception on all bands. Until recently all of my scanners are GRE. They are known for sensitivity, but more easily overload. I do have a filter between my discone and the multicoupler to remove FM. It is also a 25MHz HP filter to remove AM broadcast/etc. I feel the filter is essential before any amplification (which the multicoupler does).

Along comes multicast (simultaneous transmission of the same signal on the same frequency from multiple towers). While the PSR-500/600 still receive the signal very well, it's a roll of the dice as to whether a specific assigned voice frequency will come through in the clear. Ironically I can receive distant agencies just fine (as I likely am only receiving from a single tower). So I had to add the SDS-100 to my cache and am very happy.

My thoughts on your situation:
- I assume when you say splitter, you don't mean T
- All RG-6 coax is not created equal. Some is great and some has too much loss in UHF
- If we suspect the downlead at all, has it been measured with an ohm meter? It's not likely a direct short, but has some resistance.
- Keep in mind the best you can do running two receivers off of a single antenna is 3dB loss to each (without amplification).
- More is not always better. Why not just use the rubber antenna if it is working?
- The only sure way to get desired signal to both receivers from a single antenna is filter, Multicoupler (amp/splitter).
- Once you have desired signal to
BC325P2 it may make it worse as described above (time for an SDR or SDS).
 

OntFF221

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I run a stereo feed for Broadcastify - Left channel (GRE) for Police and EMS; Right for Fire... if I can't sort out this issue; the short term fix is move analog fire over to the GRE, and just run the Uniden for the regional system. It'll work; although not as 'clean' as I'd like.

I can't get much in the way of analog fire off the rubber antenna.... hence the desire for the discone (greater height, greater reach, etc etc)

Splitter is a TV/Coax 1:2 split, so about 3.5dB loss per side. Again, not ideal; but was working with what I had when I put this together...

I'll look into multi-couplers; but if the Discone directly into the scanner doesn't receive (or at least doesn't decode) - I'm thinking that's not the issue.

When it comes to simulcast, I'm basically a complete newbie... Is there a way to configure the scanner to isolate a single tower?
 

Ubbe

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- The 770 Mhz P2Ph2 system is simulcast. One tower is 3 km away to the SSW; other 2 are about 18-20 km. One tower is due East, one is North-West.
Is there a way to configure the scanner to isolate a single tower?
It's almost certain that you experiance simulcast problems. Several sites are using the exact same frequency and a standard scanner can't isolate one tower from the other and they interfere with each other. The stronger signal you get, and then you also receive several towers with a higher signal strenght, the worse it will get. That's why a little rubber antenna works best as it only will receives the closest site.

You either need a $600 SDS100/200 scanner or a $20 SDR dongle and some suitable PC program to decode and listen to the different talkgroups.

You could try to enable the attenuator in the scanner that do the 700MHz feed and/or put one additional external attenuator to that scanner, preferable an adjustable one to set the best attenuation where it will only receive one site clearly and the others will be too weak to be received.

/Ubbe
 
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