RadioReference on Facebook   RadioReference on Twitter   RadioReference Blog
 

Go Back   The RadioReference.com Forums > Topic Specific Forums > Antennas and Associated Hardware > Scanner / Receiver Antennas

Scanner / Receiver Antennas For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 08-13-2011, 11:32 PM
tcg tcg is offline
Member
   
Join Date: Aug 2006
Location: Algonac MI
Posts: 103
Default ST2 Antenna digital 800MHz

Ok, I'm slowly getting the bugs worked out of a used Uniden BC796D. I got the thing programmed but now I am having an interesting (to me anyhow) antenna problem.

I have a Scantenna or ST2 installed outside on a 37' mast. Until I got this scanner I was using an old RS Pro-2030 scanner to provide a feed on RR of the marine frequencies. With that antenna I can easily get 30+ mile radius.

When I hook up the ST2 to the digital scanner the marine frequencies are great. 154.000 - 162.000. The digital 800MHz stuff is crap.

Just for fun I put an old telescoping antenna on the scanner and now it is scanning great. Digital stuff loud and clear but with that antenna I lose almost all reception on the marine stuff.

I get great reception on the 800MHz stuff even without an antenna attached.

Why is that? And is there a solution. I was thinking a splitter and just hooking up both antennas but I have read enough in here to suggest that is probablly not the best solution.

Thanks
Reply With Quote
Sponsored links
  #2 (permalink)  
Old 08-14-2011, 1:42 AM
Member
   
Join Date: Apr 2009
Location: Indiana
Posts: 18
Default

I have a ST-2 with a Radio Shack 800 mobile antenna mounted on it with a catv splitter. It works just fine it started out as an experiment to see if it would work and it does.
Reply With Quote
  #3 (permalink)  
Old 08-14-2011, 1:43 AM
Member
   
Join Date: Jan 2008
Posts: 498
Default

I would try pointing the antenna at your closest tower. The ST2 might be directional, but I'm not sure about that. I have a Radio Shack version of that antenna, and hooked it up to my PRO-96. It works for the Detroit area MPSCS system, but the signal strength was all over the place.
__________________
Chuck in Detroit / NODAK 1
Reply With Quote
  #4 (permalink)  
Old 08-14-2011, 2:13 AM
n5ims's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2004
Posts: 2,999
Default

What's probably going on is with the new antenna you're having multi-path issues with the digital system due to too much signal (yes, this is possible). I suspect that the digital system is the "St. Clair County Simulcast Site" on the MPSCS (Michigan Public Safety Communications System (MPSCS) Trunking System, Statewide, Multi-State - Scanner Frequencies).

A "Simulcast Site" transmits on the same frequencies from multiple towers to increase handheld radio coverage. The system's radios have complex (and expensive) circuits to sort out the various signals and only allow the strongest to be processed. Scanners do not have these circuits and the various signals all mix together with problematic results. The more strong signals you get, the worse your receiption is. This is why things work fine with just the old telescoping antenna or even with no antenna, but work poorly with the outside antenna.

See my post here (http://forums.radioreference.com/ant...ml#post1585927) for an explaination on how and why this may be happening. I include a few things that may help as well.
Reply With Quote
  #5 (permalink)  
Old 08-14-2011, 10:52 AM
tcg tcg is offline
Member
   
Join Date: Aug 2006
Location: Algonac MI
Posts: 103
Default

Quote:
Originally Posted by n5ims View Post
What's probably going on is with the new antenna you're having multi-path issues with the digital system due to too much signal (yes, this is possible). I suspect that the digital system is the "St. Clair County Simulcast Site" on the MPSCS (Michigan Public Safety Communications System (MPSCS) Trunking System, Statewide, Multi-State - Scanner Frequencies).

A "Simulcast Site" transmits on the same frequencies from multiple towers to increase handheld radio coverage. The system's radios have complex (and expensive) circuits to sort out the various signals and only allow the strongest to be processed. Scanners do not have these circuits and the various signals all mix together with problematic results. The more strong signals you get, the worse your receiption is. This is why things work fine with just the old telescoping antenna or even with no antenna, but work poorly with the outside antenna.

See my post here (http://forums.radioreference.com/ant...ml#post1585927) for an explaination on how and why this may be happening. I include a few things that may help as well.
I read your other response and it all makes sense.

My scanner only allows setting the attenuator in conventional mode not trunking.

The reason I picked up the digital scanner was to enhance my live feed that scans marine related stuff. There are a few talkgroups of our local marine division. I need an antenna to pick up both the marine frequencies, 154.000 - 164.000. And the 800MHz stuff.

Would a possible option be two antennas? A dedicated marine antenna, like the ones mounted on boats, mounted at the top of my mast and an 800MHz mounted below it but not as high?

I did see this ATT-20 Variable Attenuator and wonder if it might be a possible solution. It would be cheaper than purchasing 2 new antennas.

Thanks for the help.
Reply With Quote
Sponsored links
  #6 (permalink)  
Old 08-14-2011, 1:09 PM
rfradioconsult's Avatar
Member
   
Join Date: Dec 2004
Location: Tulsa
Posts: 1,124
Default

The design of the ST2 does not favor 800 MHz reception; for VHF-lowband, hiband and UHF it works very well. However the physical characteristics severally limt its performance on 800. The element lengths present multiple wave lengths at 800 and the radiation pattern tends to create the major lobes toward the antenna ends as opposed to the preferred side-lobe pattern.
Reply With Quote
  #7 (permalink)  
Old 08-14-2011, 1:36 PM
MICOM's Avatar
Member
  Audio Feed Provider
Audio Feed Provider
 
Join Date: Sep 2010
Location: Chesterfield, MI
Posts: 2
Default

TCG,
Did you get my PM?
MICOM
Reply With Quote
  #8 (permalink)  
Old 08-14-2011, 2:58 PM
Member
   
Join Date: Aug 2006
Location: South Jersey
Posts: 885
Default

Quote:
Originally Posted by ppremc View Post
I have a ST-2 with a Radio Shack 800 mobile antenna mounted on it with a catv splitter. It works just fine it started out as an experiment to see if it would work and it does.
That sounds very interesting. Could you post a sketch (picture would be great if you can manage it) of it? Particularly interested in how the 800 if mounted/connected.

Thanks.

Amp
Reply With Quote
  #9 (permalink)  
Old 08-14-2011, 5:22 PM
tcg tcg is offline
Member
   
Join Date: Aug 2006
Location: Algonac MI
Posts: 103
Default

Quote:
Originally Posted by ppremc View Post
I have a ST-2 with a Radio Shack 800 mobile antenna mounted on it with a catv splitter. It works just fine it started out as an experiment to see if it would work and it does.
I'm interested in how that would solve my problem of too much signal. It seems if were to do the same thing the ST2 would still be interfering with the 800MHz stuff.
Reply With Quote
Sponsored links
  #10 (permalink)  
Old 08-14-2011, 5:23 PM
tcg tcg is offline
Member
   
Join Date: Aug 2006
Location: Algonac MI
Posts: 103
Default

Quote:
Originally Posted by MICOM View Post
TCG,
Did you get my PM?
MICOM
Yes I did and I responded. Not sure how I missed your PM.

Thank You.
Reply With Quote
  #11 (permalink)  
Old 08-14-2011, 6:04 PM
n5ims's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2004
Posts: 2,999
Default

This will probably be a difficult problem to solve since you need a good signal on the marine bands, but want to really limit the signal strength on 800 MHz.

One option may be to get a filter that will pass the marine band frequencies but not the 800 MHz ones (generally called a "bandpass filter"). What it will do is to freely pass the desired range of frequencies while greatly reducing the level of signals outside of that range. While normally this would virtually eliminate the 800 MHz band signal, since you get it fine even without an antenna there may be enough signal strength to get the job done. Check with PAR Electronics to see what they might recommend (PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts). They have some standard filters but also make custom ones. Talking to them on the phone and explaining your situation may let them find a good solution for you.

Another option might be to get a single-band antenna that covers the Marine Band specifically (which might limit the 800 MHz signal strength since it's pretty far out-of-band). Then select a type of coax that has fair loss numbers at 160 MHz, but really poor loss numbers at 800 MHz. That might get you the performance you need on the Marine Band and limited signal strength at 800 MHz. You can check the numbers with this on-line calculator Coax Loss Calculator to see what type(s) may do the necessary job. I suspect that RG-58 may be an option (just under 3 dB at 160 MHz and over 7 dB at 860 MHz).
Reply With Quote
  #12 (permalink)  
Old 08-15-2011, 6:56 PM
tcg tcg is offline
Member
   
Join Date: Aug 2006
Location: Algonac MI
Posts: 103
Default

With the help of a RR member who called me, we had a very nice talk, I solved my 800 reception issues.

Here is what I have learned so far. It was suggested I should try taking a coax cable and stripping off 3.5" of shielding exposing the copper lead and sticking that outside. I had a second coax cable leading outside from an old tv antenna install so I gave it a try.

Last night I just hung the exposed cable over a second story balcony rail and my reception improved a lot. Today I tried mounting that same cable half way up my mast about 7 or 8 feet below my ST2. The garbled and broken reception returned.

I then took out a very nice map of the tower locations my RR helper sent me drew some bearing lines and got out a compass. I then mounted the cable much lower and in line of sight of two towers. One is about 3 miles away the other is about 9 miles. Two different county systems.

I am getting excellent reception.

I will now research 800MHz antennas or I just may keep using my free homemade antenna.

First chance I get I will be replacing the ST2 or adding a dedicated marine band antenna. My wife loves it when I get out the ladder and lean it against the tree off our second story balcony and then climb almost 40' up. She always ups my life insurance first. I quit letting her hold the ladder. I think she shakes it on purpose.

Thanks for the tips and help.
Reply With Quote
  #13 (permalink)  
Old 09-05-2011, 4:14 AM
rma0100's Avatar
Member
   
Join Date: Dec 2004
Location: Tewksbury, MA
Posts: 58
Default

I was challenged by the sales manager of Scanner Master to beat their prices. I just ordered the reinforced ST2 Scanner Antenna from GDI Electronics for $27.82. Scanner Master's price is $59.99. In these economic times it's a wise move to do comparison shopping on the net before buying anything. Check ebay as well. Their LMR 400 cable is also more. Their Multicouplers are also more. Their 996XT price is also more.The ST2 Scanner Antenna is one of the best scanner antennas money can buy and for short money as well. The original model called the Scantenna was also extremely good buy quite flimsy and I didn't think it would hold up under strong wind conditions but it did and I assume the new ST2 will be even stronger. The antenna comes with the cable and the proper connectors. You just can't beat that price and I have antennas that cost me well over $200 and they only perform a bit better on some frequencies. A lot of HAMS will critisize the antenna because its impedance is 75 Ohms but it performs very well for receive all across the band. I've owned several of them and as you will read here in the forums, it's a solid performer. When buying anything do your homework and be wary when they tell you they have the lowest price...they all seem to say that. Google will perform price comparisons for you and also be wary of those who make up with their low pricing with added cost to shipping. Our current economic times dictate that a smart shopper does his homework. Scanner World is also a good place to look for good deals. it's called capitalism!
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 9:22 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
All information here is Copyright 2012 by RadioReference.com LLC and Lindsay C. Blanton III.Ad Management by RedTyger
Copyright 2011 by RadioReference.com LLC Privacy Policy  |  Terms and Conditions