Terrible intermod with noaa weather repeater

[kruser]

That would only be effective under two conditions:

1. It's placed IN FRONT OF any active devices i.e preamps.

2. The interfering signals are outside the pass-band of the filter. If it's a notch filter, the notch has to be tuned to the frequency that's causing the overload condition and narrow enough to not filter out the desired signals.

The PAR filter for 162 MHz will pass power so it can be placed after a coax powered amp. I assume all the PAR scanner type filters are the same. I have the 152, 158 and 162 filters as well as a custom 930 MHz filter and they all pass DC.

The 162 PAR notch filter "may" help (I really doubt it will though) with the OP's wx intermod but that is about it. He is still going to experience severe overload, intermodulation distortion etc if he insists on using the amplified TV antenna as has been pointed out in the thread several times already.

The antenna the OP is using is about the worst antenna one could ever hook to a scanner.
I had the same antenna but hooked to my TV's as it was intended for. I was searching the bands one day with the scanners and kept finding what appeared to be birdies but I knew they were from an outside source.
I made a list and started powering things down. It was that darn amplified antenna radiating tons of trash from its own oscillator!
I junked the thing and ended up with an unamplified antenna for OTA and then I use an inline bullet amp when I do need amplification of OTA stations.


To the OP, what everyone has said is very true. What you are using for an antenna is going to cause WAY more issues than any benefit it will ever give.
Why do you think that your scanners S-meter is showing full bars at times even though there is no signal? That is a product of the cheap and noisy amplifier inside the antenna you are using and also a sign of overload of the scanner.
You will never get rid of the problems you are complaining of if you insist on using a TV or so called HDTV antenna that has an amplifier built in period.

Can you construct a wire dipole cut for the VHF range mounted under maybe one eave of your home? Something that is not really visible.
It would need to be vertical still but would work better than what you are using now plus it would at least get your antenna outside of the building and away from your noise generators like computers and computer accessories (modems, routers etc..) and TV's etc.
Before I could have an antenna on my apartment roof, I found that a simple magnet mount multi-band scanner antenna out on my balcony did a much better job over the stock antenna that came with the scanner.
Even setting a mobile antenna in a window that faces the signals direction can make a huge difference.

You may need to get creative with figuring out how to build and install some kind of antenna that does not look like an antenna. Using an amplified TV antenna like you are using now is going to cause big problems as you are already finding out.
There are books published for amateur radio operators that live in apartments or, god forbid, a HOA area with antenna restrictions. These books discuss how to build effective antennas for those in your exact situation. I think the ARRL even publishes one. Something like "Antennas for apartment dwellers" for example. You are not in an apartment but the same rules apply.
Almost all the V/UHF antennas in these books can be altered so they are more effective for the typical scanner frequency ranges.
Doing something like that is going to work better than trying to use your current setup.
You can try the PAR model VHFSYM(162)HT and it 'may' eliminate the intermod for the NOAA channel but as other transmitters come on, they are just going to mix and cause many other intermod products when using your current antenna. You will fight it until the day you get rid of that antenna.

Good luck with whatever you try!

 

[gewecke]

The built in, channel by channel attenuation does help cut down on it... but not totally eliminate it, plus I have to be quick on the ATT button, especially if i'm across the room when it happens

Do you think getting a higher quality injector or a preamp would help?

Do not use a preamp at all,you shouldn't need it.


73,
n9zas

 

[zz0468]

The PAR filter for 162 MHz will pass power so it can be placed after a coax powered amp. I assume all the PAR scanner type filters are the same. I have the 152, 158 and 162 filters as well as a custom 930 MHz filter and they all pass DC.

They might well pass DC, but that's not the issue. If the preamp at the antenna is the device getting overloaded and creating the intermod, putting the filter AFTER the antenna won't solve the problem. To be effective, a filter MUST be put in front of any active devices.

 

[gewecke]

More criticism with no real solutions. And I wonder why my other friends avoid these forums like the plague.

The correct advice was given, ditch the preamp. That is the likely source of your problem since the NWS station is 5 miles from you. Have you considered a inside antenna of better quality? There ARE several antennas you can use with success inside your house!
If you have central air or a window ac unit, magnetic mount antennas can be mounted on those with good results too! We are NOT criticizing you,but trying to help!

73,
n9zas

 

[k3cfc]

more criticism with no real solutions. And i wonder why my other friends avoid these forums like the plague.

here is a solution. Get a job buy a farm with 100 acre woods and put up an antenna array. Problem solved.

 

[jim202]

More criticism with no real solutions. And I wonder why my other friends avoid these forums like the plague.

Look, people are trying to tell you that your pre amp is causing the intermod problems. If you call that criticism, so be it. There are some of us that have been in this radio service field for well over 40 years. If you don't want to listen to our help. then why are you persisting to continue this thread.

You have been told by a number of people what the solution is. If you won't take their advice, then so be it.

 

[kjvonly1611]

I've been letting this go a while to see if there is any "positive" feedback, and there is some which I appreciate. My park rules specifically state the only type of visible antenna allowed are satellite TV antenna, and even they have to be less than 36". I would like to go outdoors with the antenna and like the ventenna concept though they don't seem to have a wide-range setup. I could probably get away with doing the mag mount on the A/C unit, just not in the winter (most of the year ) plus that would involve hoping my neighbor doesn't know the antenna rule as the rule doesn't specify "roof mounted"...

Buying a 100 acre ranch simply ain't an option as my wife is a stay at home mom and my income alone has to support her and the children, pay taxes, pay for homeschooling, support hobbies, etc...

I already live in the country which is why I need something decent or my scanners would never pick up anything but the locals. BTW, for you Uniden fans out there, my RS Pro-97 does not have the intermod problem.... but it's not digital either

I like to tinker, which is why I have my current setup, you can't see it from the road making is "semi-legal". I've toyed with the idea of a homemade dipole or j-pole laying flat on the roof (read: not upright). I don't like to do things the conventional way as I'm sure many of you Hams can appreciate, something i've considered becoming myself.

A little update: I have found that turning the antenna to face North/South cuts down on 80% of the intermod. The weather repeater is West-North-West of me (and actually only 2.4 linear miles away)... The antenna was pointed North-West when it was getting more problems, so this antenna IS directional (something not mentioned in it's literature). Due to polarization differences I've considered laying the antenna flat but haven't yet because I'm still tested it.

I've been in the hobby for roughly 25 years (i'm 37 and grew up with scanners in my home) but was out for 5 due to a move, stuff in storage, etc... In that time my whole state's PD went digital (some, but few already were) so I just recently picked up this 396T from a friend.

Anyways, just some background and progress for ya.

 

[zz0468]

I've been letting this go a while to see if there is any "positive" feedback, and there is some which I appreciate.

There's been a ton of positive feedback. Trouble is, it's apparently not what you've wanted to hear. Your situation seems to require a sub-optimal solution, so it becomes up to you to decide where and how much to compromise your reception to accommodate the strict restrictions at your park.

My park rules specifically state the only type of visible antenna allowed are satellite TV antenna, and even they have to be less than 36". I would like to go outdoors with the antenna and like the ventenna concept though they don't seem to have a wide-range setup.

Real 'wide-range' antennas are usually pretty bulky and come in the form of log-periodics, and discones. These are clearly outside the scope of stealth antennas, so forget that. The next most likely candidate is an active antenna. You have one, but it's not satisfactory, or you wouldn't have made this post.

I already live in the country which is why I need something decent or my scanners would never pick up anything but the locals.

Ok, but you've already ruled out anything "decent". You'll have to listen to suggestions for something not decent, that maybe can be made to work 'good enough'.

I like to tinker, which is why I have my current setup, you can't see it from the road making is "semi-legal". I've toyed with the idea of a homemade dipole or j-pole laying flat on the roof (read: not upright).

A j-pole is, by definition, a relatively narrow band antenna, so you either have to rule that type of antenna out, or rule out the wide-band requirement. The two are mutually exclusive. Sorry, it's those pesky laws of physics again.

Lying it flat on the roof will do two things. You'll have a minimum of 20 db of cross-polarity loss, most, if not all, signals you want to listen to are horizontally polarized. being in close proximity to the roof, laying flat, will likely inhibit the antenna's ability to intercept signals effectively, and add a considerable amount of loss to the 20 db you
ll be starting with.

Should work great on solving that intermod problem, though.

I don't like to do things the conventional way as I'm sure many of you Hams can appreciate, something i've considered becoming myself.

That's fine, but antenna theory is pretty mature, and there's not a whole lot new under the sun that hasn't effectively violated the laws of physics. Unconventional solutions usually end up being conventional compromises.

A little update: I have found that turning the antenna to face North/South cuts down on 80% of the intermod. The weather repeater is West-North-West of me (and actually only 2.4 linear miles away)... The antenna was pointed North-West when it was getting more problems, so this antenna IS directional (something not mentioned in it's literature).

This sounds like a good indicator that the amplifier built into the antenna is the culprit in generating the intermod. With the weather transmitter that close, it's quite likely that's the predominant source of energy that is overloading the preamp located inside the antenna.

My suggestion? Find one of those cheap NMO ground plane kits and an 18" whip for it. They're easy to install, work pretty good, and are nearly impossible to see from any distance. If you find you need a preamp, then get one from Advanced Receiver Research. Install the preamp inside, near the scanner. If adding the preamp causes more intermod, then order a 162 MHz notch filter from PAR.

You'll have all the compromises covered... half decent performance, not really visible, not truly 'wide band', but not really prone to interference either, and configured in a manner that you can apply various tools to cure intermod.

 

[aries6263]

Check Ebay for a filter

Here is the link

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

 

[nanZor]

Hmm... how about just placing a multiband duck like a Diamond RH77 or equivalent inside a plastic owl outside? No antenna there. Disguise the antenna as something else.

At the end of the day, you are still interfacing to a handheld radio, not expressly designed for major outdoor antenna systems. Yes, it can be done, but don't go bananas if you experience overload / desense. In this case, less is more.