I Discovered The Secret to ELIMINATING Interference
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- เผยแพร่เมื่อ 1 ส.ค. 2024
- Do you suffer from squeaks, squawks and other interference? This bandpass filter for the 2m band may just be the solution for you! Perfect for repeaters located on high power broadcast transmitter sites.
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⏱️Chapters⏱️
0:00 Weird Interference
0:48 What is a bandpass filter?
4:10 OCI Filters (2m, 1.25m & 70cm)
05:58 Sweeping the filter
09:58 How well does it work?
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This issue began appearing in the 1980s, when the Japanese manufacturers began expanding the frequency bandwidth of the mobile radio receivers. Savvy operators embraced the Kenwood TM-2530, 2550, and 2570 mobiles as they were relatively immune to intermodulation, cross mod, and blocking from the high-powered paging transmitters.
I remember my business Motorola HT from the 1980's. It rejected all but the UHF repeater while I was standing on the skyscraper rooftop where the FM transmit antennas and a TV antenna were. A regular radio would surely have de-sensed or overloaded. For the noobs, keep this in mind when you purchase a radio that has a very wide bandwidth. In order to hear all these bands, many manufacturers cut corners in the filters, so you'll probably need to add an external filter if you're in a moderate RF location. 73
I hear a newbie trying to run a Baofeng on an outside antenna from time to time, and it never goes well.
My Tempo S1 (AOR AR240) handy 1978 covered 140 to 150MHz with little blocking,
it was one of the first handys with a varicap tuned front end. Icom copied it with
the IC2A, but they used a wide fixed tuned front end.
Wow made in Canada with Robertson screws 🙂
- VE2HEW
When a lot of the broadband 2M rigs came out in the 90's they suffered badly from pager network interference, yet the older IC22S, with its helical resonators in the front end was rarely bothered by them.
That looks like a really nicely made filter. I've been looking for an AM broadcast band filter that preferably doesn't also knock out 160M
Combline filter? Ahhhh the "black arts" of VHF. What is the power capacity through it (EME so it must be high?). Thanks for the vid informative and educational. 73 de VK2AOE
160W
Nooelect makes a bunch of nice bandpass filters. I have all the weather satellites on one. Its catching a few weather satellites images now and I have a FM radio bandpass all inline and one with a bias T if you want. They rub 20-30 USD each and work really well.
Howdy Hayden. theres a company here called Morgan Systems that make excellent filters for 80m, 40m, 20m, 10m,. etc. they are high quality so tend to be a little pricey. I bought one of their AM Broadcast Filters because of interference from a local 1KW AM Station that was making a bunch of noise on 40m and 20m. works beautifully.
Nice! I'll check them out
most repeaters i saw used. cavity type units and circulators too
I ordered one of these today. when it comes in we will definitely put it to the test👍🏽👍🏽👍🏽👍🏽
Cool 👍
It's very shiny !
;)
Very very shiny
Great video Hayden! 73
Thanks mate!
Thank you Hayden :-)
You're welcome!
Great video, you've also reminded me that I need to zero my setup and cabling on my hp more often 😂.
Shame its not as sharp on the high end with its roll off... I get some bad pager tx intetmod here.
Hopefully this filter doesn't suffer the problems with vibration flat pack duplexors do and go out of tune.
To conclude, the real test will be PIM on the repeater. 👍
Cheers
VK2VRK
Thanks mate. Yeah obviously with it needing to cover the whole of 2m, pagers at 148 MHz aren't as attentuated... a separate notch is probably better for that.
Honestly, without opening up the filter - I don't think there will be that much vibration issues.
Just waiting for the snow to melt before getting it up on the mountain!
Yeah I'd be interested to see what a sweep of the spectrum looks like once you go onsite on a analyser...
A notch, yes well too much filtration will obviously have too much loss..
I'll be watching this one with keen interest.
Damn gas stations here in Utah are so full of RFI.
Microprocessor noise. When this started in the 1990s we called the myriad carriers and noises "space invaders" after the video game, and because they were invading our space.
So when do you try it out on your repeater ?
I had a similar issue with high power TV transmitters at the same site and found that added filtering did not help because the problem was low level wideband noise from the TV tx. No cure possible except at source.
I'll try it out once the snow melts.
Its quite large but I guess it handles alot of power and filters well.
160W
In Vienna we have a TV propaganda broadcast transmitter at about 498MHz causing problems to all those cheap direct sampling receiver radios. You can fix that with a bandpass filter.. or you buy a radio with a superheterodyne receiver. 😁
Don't void the warranty.😂
just a band pass filter
Yep, band pass/ band reject. I had to buy a FM filter for my scanner because of interference from 96.9.
If you want to see something amazing take a look at how much harmonic attenuation a simple antenna tuner gives.