Change in reception

[Techy]

I had recently did a brand new install of a Grove Omni antenna for my base scanners.
I used a Channel Master 94444 300/75 ohm matching transformer, Radio Shack RG-6 dual shield coax at say, maybe a 35-40ft run. All connections from the balun are waterproofed and sealed. At the static discharge unit is all waterproofed and sealed. But my reception was perfect a few weeks ago. Now as of this past week it seems the reception has turned lousy. I monitor the Suffolk County, NY TRS. My signal meters on the BCT15X and my GRE-PSR-410 all show lower than what it was. Makes for noisy monitoring. I am STUMPED on as to why it went somewhat deaf. I pop on the original antenna or the RS 800Mhz duck and it performs perfect. Could the balun be bad by some chance?

Edit: Forgot to mention all coax ends are RG-6 compression. Coax was tested as well for any shorts before it went up. No shorts at all.

 

[WA0CBW]

How about opens? Is the center conductor even with the end of the connector? Or is it too short (thus producing an open)?

Is the Grove omni antenna 300 Ohms? I'm guessing that is where the balun is; between the antenna and the coax.

BB

 

[Techy]

WA0CBW, the ends are even with the F connectors. The foam dielectric is even as well at the bottom inners of the F connectors. No loose braid touching no place when the compression fittings were installed. Im anal about that stuff lol. And yes sir the Grove omni is a 300 ohm antenna. Off center fed dipole. It performed perfect the first few weeks, then I noticed the reception start falling off. Im really starting to think the balun may be bad somehow. And thank you for the input as well. Im truley stumped. I have not suffered any storms or lightning near me at all. Plus I always disconnect the antenna from the scanner anyway during bad lightning.

 

[kb2vxa]

Hmmm, I'm wondering why if you suspect the balun you don't replace it and see what happens. All we can do is guess, you're where the action is. Process of elimination finds the culprit so it's a 1 out of 4 chance, antenna, balun, F connector 1 and F connector 2.

Here's a hint, a waterproofed balun never goes bad so if that's the one make sure you cover the new one with Plasti Dip available at Home Despot and other fine stores. Just because it's an outdoor balun doesn't say it's waterproof, I know those things and see where water can enter by capillary action. While you're at it coat the outdoor F connector too, Rat Shack sure as shootin' doesn't use the high quality connectors the cable TV company does.

"Plus I always disconnect the antenna from the scanner anyway during bad lightning."

Good lightning can turn bad when it hits so take no chances.

 

[Techy]

Thanks Warren for the tips. Im awaiting the new balun now. I will pick up some of the plastic coating to dip the balun and F connector in when I get it. Hopefully it will resume as it was. Keeping my fingers and toes crossed lol. :lol:

 

[kf5bti]

When you say you put on the original antenna was this outside using the same coax? If so you have ruled out the coax and connectors leaving only the antenna itself and balun.

 

[WA0CBW]

I would suggest the balun as well. The balun can be kind of fragile especially the crimped on spade lugs. One of them might have broken in the wind.

BB

 

[jackj]

Your problem could be anywhere between the antenna and the radio. An ohm meter will help you, check for shorts and opens with the coax and antenna. Your balun will, I believe, show a short between the 300 ohm leads. It may also show a short between the 300 ohm side and the 75 ohm leads. There are a couple of different designs that could be used for a balun.

A lightning strike several hundred yards away could induce enough current into the antenna to arc over inside the coax or the balun and not show anything on the outside. Good luck.

 

[Techy]

Thanks jack, I will try those tips with the meter. The new balun should be here on Thursday.
I have double checked the coax and connectors and it all seems fine. I tried to use the best in everything on this install. Belden snap/seal RG-6 compression connectors. Belden static discharge unit at point of house entry. All ends inside were waterproofed using a dielectric paste called STUF, to help against any water intrusion. The antenna is brand new. Thing is it worked fine the first few weeks and then just dropped off. Im in an area thats not saturated with strong transmitters near by at all. Im more in the boonies so to speak lol. I will let you guys know how it goes with the new balun when it arrives. Thanks again to those that helped, I really appreciate it alot.

 

[LtDoc]

The 'simple' answer is to determine what changed, and why. It could be any one of the things between the receiver and the antenna, or the receiver or the antenna, or a combination of several things.
there are two basic ways of checking things, measure it, or substitute it. Neither are 'simple' (or cheap), but that's what all 'trouble shooting' consists of.
Nothing new in any of this, but sometimes restating the problem helps.
- 'Doc

 

[oilmillcharlie]

Is there a possibility that you have improved the reception with the new antenna to the point that you are getting signal overload de-sensing the radio? I would check to see if attenuating the radio helps or not.

B.K.

 

[Techy]

LtDoc thanks for the input, Charlie when the ATT is on, it knocks it down to 0 signal received.
No de-sensing at all. But the wackiest thing is, VHF-Hi and VHF-Lo bands come through ok. It seems the trunked system that I monitor took the hit. Standard Moto type 2, 6 sight simulcast system. It comes in very staticy for some reason.The balun I use is a Channel Master CM 94444. I heard it was a better one for the money over the cheezy ones that I had here. The last cheezy one that granny used on her old TV antenna was loaded with water. This one will be dipped in plasti-coat as Warren mentioned. I will post back when the new one is installed again. Just need time to get up on the roof again and test and install it again sheeesh.

 

[rfking123]

Tray a different BALUN. They be bad, or work well.

 

[scanmanmi]

Weeellllllllllllllll? My Rat Shack ground plane quit working. I got out my telescope (yes telescope) and can see the center conductor on the antenna pulled out. It's 30 feet and I can't get to it.

 

[Techy]

Well I made it on the roof and changed the balun out, replaced with a new one that has been dipped in plasti-coat. I must report reception is back on par!! Yahoo lol. :lol: I had emailed Channel Master's tech support and they did indeed say, water/rain can creep inside of it. I want to try to crack open the old one, but it seems so tight I can't even split it open to see.
Plus I was told to keep the leads as close to each other as possible. This balun has pigtail leads and not the small section of twin lead. That has made some increase in my reception today. So if any of you purchase a channel master 94444 balun, keep the pigtail leads to the thumbscrews as close together as possible and not to spread them wide apart. Im just glad it wasn't the coax run... Thanks again to all those that helped me here. My best regards.

 

[reconrider8]

question techy. what did you use to set that antenna off the mast in your pic im looking for something to do that with my 800 omni when i get it up so its not sitting right on my mast

 

[Techy]

Hi recon bro, that antenna was made that way. It has a square aluminum boom that contains the U-Bolt to mount it and the dipole out front.

 

[majoco]

A simple fault finding idea. When you install an open circuit antenna such as a discone or dipole without a balun, fit a 4.7kohm resistor across the terminals. Then with a quick check with your meter at the receiver end of the coax, you should see the 4.7k. can't see it? or it's open or short, you got a problem.

Another easy piece of testing equipment is a coax plug with a resistor in it - same principle!