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 Low Pass Filters (for cb).?

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Tristar
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Tristar

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PostSubject: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeWed Mar 03, 2021 5:37 pm

Hi 🙋‍� 
I wasn’t sure exactly where this should go so if there’s a better page please feel free to move it on. Thanks. 

I’ve been reading and watching YT about low pass filters and wondered if people are still using them to reduce harmonics interference on other bands or electronic equipment nearby?

If so which make are you using?

Many thanks 

John

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2TX240
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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeWed Mar 03, 2021 6:38 pm

I actually run one on each antenna... just because.

I.C.E 421 HF Low Pass filters.

I had them from my previous QTH, so I put them back up

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Seasick
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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeWed Mar 03, 2021 6:46 pm

I use to run low pass, or band pass,  filters on all of my radios at one time. I lived close to the perimeter fence of a airfield & it saved me from being accused of anything. 

I also ran band pass on my ADS receiver, before they stopped taking input from windows. It made my RX work a lot better.

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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeWed Mar 03, 2021 9:58 pm

I’m not, so sorry can’t help on makes. Am not running any additional power at home either, only what the transceiver itself can put out, and although insertion loss is probably negligible it would irk me knowing I would be losing anything of my limited power by putting one inline. I would of course though if a neighbour said to me they were having problems.

I have ferrited the power cables though as that helps stop interference incoming and outgoing over the mains.

Do CBs still cause interference to TVs and other things much now though? Seems to be more the other way round since I’ve come back to this.

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Tristar
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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeWed Mar 03, 2021 10:19 pm

From watching the videos etc they are used to prevent harmonics dropping up and down onto other bands. 
I’m told the filter can also prevent being picked up on speakers ( not like the old days where you hear every word) but it may stop clicks of the ptt switch. 
Also I’m told cb can still cause problems with wifi modems too. 

I use legal power too. 
So I don’t interfere with others as far as I know but would like to take all precautions that are reasonable. 

Thanks for people’s responses and any information on where these filters have been used in personal experience would be very helpful.

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Seasick
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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeWed Mar 03, 2021 11:10 pm

SangueG wrote:
Do CBs still cause interference to TVs and other things much now though? Seems to be more the other way round since I’ve come back to this.


Anything & everything is now, more than ever, likely to cause QRM to a TV, due to their build quality now. HOWEVER. All that normally happens now is that  the TV's screen goes blue. Where it used to be audio breakthrough, lines etc etc. With digital TV, it is far far more likely to be the screen going blue & to make things even better for us, TV repair people & so called antenna specialists, now know less than they used to. So the chances of anyone finding out what is happening is not really a problem for us now, as much as it used to be. 

A friend who runs a TV repair & TV antenna business, was telling me that an  analyser to see what is causing problems to a digital TV's signal, costs around £2000+. How many businesses are going to pay that?

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Tristar
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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeThu Mar 04, 2021 11:02 am

I’m looking at this for me as much as anyone else.
I don’t want to spoil anyone else’s pleasure of listening to music or watching tv because of my hobby if it can be prevented.
I see it as a duty of care when I use my radio. 🤷‍�

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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeThu Mar 04, 2021 12:12 pm

Tristar wrote:
I don’t want to spoil anyone else’s pleasure of listening to music or watching tv because of my hobby if it can be prevented.


The problem is that now, most technology is built to the lowest & cheapest possible standards.  

Filters will protect others to a certain extent. Which is why when I lived close to the airfield, I used filters. It was the considerate thing to do.  But filters will only help those using well made equipment & that means not much if any domestic electronics & only some commercial equipment. Your best protection against your equipment being the cause of interference is a wave absorption meter. Check for unwanted RF on unwanted frequencies. 

I do not know about now, but when the GPO/DTI visited a radio amateur. An absorption wave meter, was one of the first things they asked to see. 

Back in the early 80's I think it was. A new legal FM station in London received a complaint from either Gatwick or  Heathrow complaining about interference to aircraft landing there. The resulting investigation was widely reported in the amateur/swl community. As it said that the broadcast transmitter was clean & well filtered, but that multi million pound aircraft,  which had radios that needed to work properly, were fitted with poorly designed radios not capable of working safely in the real world. Another incident around the same time found that GCHQ, who had  made a complaint against another broadcast station. Had not maintained it's equipment for years. So GCHQ was shouting national security is at risk, but a spark, with a paint brush solved the so called interference problem by simply  dusting the inside of the radio receivers.

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Tristar
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Tristar

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Low Pass Filters (for cb).? Empty
PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeFri Mar 26, 2021 9:06 am

Well I decided to put one in line. It hasn’t effected the swr and power lose is minimal.
It’s in line and I don’t even know it’s there so why not.
Many thanks for your answers and thoughts.
Much appreciated!

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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeMon Apr 19, 2021 10:53 am

Fortunately enough, it is not something I have had an issue with this time around, the positioning of my antenna is away from the house and more importantly the houses of others and in the advent of the digital age, many peoples televisions are no longer used as receivers but as monitors for cable boxes, satellite receivers smart TV devices etc. 
 
The electronics have improved too, changed would probably be a better term, there doesn't seem to be so many items that can be directly affected in daily use around us, if you think back we had cordless phones, baby monitors, remote control devices and a whole host of items using 27MHZ alongside the C.B. bands and you just dont see as many of them in daily use around us any more.

It is the endless wireless technology and LED lighting which appears to cause interference with our radios I find has been my own experience, I was able to remedy this in part, at least, using ferrite rings on the power leads of the worst offending items.
I opted for mix 31 and 43 at first having had little success but then I noticed in the first licence manual I hadn't wound it correctly, after correcting the way it was wound it reduced my nose floor by 3-5 S points across the HF bands including 11m of course and it really cleared things up on 144MHZ and the PMR frequencies allowing me to hear a friend on his handy in a nearby village where I couldn't make him out clearly at all for the QRM that came in with his signal.

Being a great believer in "If it ain't broke dont fix it" I will leave well alone but should I have any issues in the future I most certainly know where to look and I am sure this will prove invaluable information for those on a quest to eliminate interference from our stations.

73's

Alan

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Tristar
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PostSubject: Re: Low Pass Filters (for cb).?   Low Pass Filters (for cb).? Icon_minitimeSat May 01, 2021 10:33 am

Hi
Just a quick update.
I’ve put a kenwood low pass filter in line as I said above and had it constantly inline.
The people I talk to on a regular basis have not noticed a difference in my signal they receive so if it prevents unwanted harmonics dropping onto other bands and keeps my signal clean then I’m happy.
Thanks for all the comments guys.
Catch you on the flip flop!

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