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View Full Version : RM Italy 27/586 Low pass filters



whiteastro
02-09-2020, 04:12 PM
Was looking at my RM Italy amp hook up diagram today and seen this filter illustrated that I didn't pay attention to before. I ordered 3 of them from Walmart because they were like $28.50 ea. Question is Has anyone used these before and do they lessen your TX power? I'm not a electronics tech so don't shoot me too bad! LOL

Turboomni
02-09-2020, 07:27 PM
Interesting as I saw a youtube video on RM Italy amps and he recommended a low pass filter to reduce TVI so your neighbors won't knock on your door. I also heard that amps over driven will cause this more than amps not over driven.
He also said RM Italy sells them too as you found out. Be interested in what the experts say about these things.

JesseJamesDallas
02-09-2020, 09:18 PM
Was looking at my RM Italy amp hook up diagram today and seen this filter illustrated that I didn't pay attention to before. I ordered 3 of them from Walmart because they were like $28.50 ea. Question is Has anyone used these before and do they lessen your TX power? I'm not a electronics tech so don't shoot me too bad! LOL
Why did you order 3??? You have 3 set-ups your planning on using them on?

Anyway...If the radio has been P&T, then don't count on much performance out of a TVI filter...

I've never used a TVI filter from RM Italy, I do have a couple 1500w ones, one being a MFJ, the other one I think is a Johnson, but at any rate about the only thing I could see they did was show less watts on my watt meter...Never had much luck with TVI filters on 11 Meter....HAM guys swear by them tho.

whiteastro
02-10-2020, 08:49 AM
Interesting as I saw a youtube video on RM Italy amps and he recommended a low pass filter to reduce TVI so your neighbors won't knock on your door. I also heard that amps over driven will cause this more than amps not over driven.
He also said RM Italy sells them too as you found out. Be interested in what the experts say about these things.


I had to laugh because I might have seen that same YouTube video that you watched and more. They shouldn't be overdriven because they are the ones that RM Italy recommended. One video said they helped reduce some of the noise in the radio which is not a bad thing. Nothing ventured Nothing gained! ( Maybe Lost ) but I have lost more down the drain thru Alcohol! LOL

whiteastro
02-10-2020, 09:21 AM
Why did you order 3??? You have 3 set-ups your planning on using them on?

Anyway...If the radio has been P&T, then don't count on much performance out of a TVI filter...

I've never used a TVI filter from RM Italy, I do have a couple 1500w ones, one being a MFJ, the other one I think is a Johnson, but at any rate about the only thing I could see they did was show less watts on my watt meter...Never had much luck with TVI filters on 11 Meter....HAM guys swear by them tho.


Thanks for the comeback JJD you said something I feared ( Less Watts ) and I will be watching close for that problem. I bought 3 because I have a KL200P a KL203P, and a KL300P. The KL 200P & KL203P are for my car and van. The KL300P is for my radio bench. I live in small town with a lot of neighbors and I don't want to give them more to bitch about! ( And they Do ) I might have to save my Palomar 300A for my future country home. The other day I was playing with my Palomar on AM Channel 19 and I had a trucker comment on how he thought I was going to blow the windows out of his truck. Makes you wonder about these Old cheap neighbors and their Old TVs running a digital converter box I don't need the FCC knocking on my door if you know what I mean! They ( Filters ) didn't cost that much so if I end up not using them I'll put them with my other mountain of electronic junk LOL out for the yard sale! PS If they cut some of the noise in my radios that wouldn't hurt my feelings either!

Turboomni
02-10-2020, 10:46 AM
What I meant was if the amps are over driven by a cb radio with too much output they will make more noise and possibly piss off the neighborhood.

whiteastro
02-10-2020, 12:19 PM
What I meant was if the amps are over driven by a cb radio with too much output they will make more noise and possibly piss off the neighborhood.

I always make sure my wattage output on my cb is turned down before I turn on my amp. I can't afford to fry any of my equipment. The 980 is automatic low drive and my 2 979s both have adjustments for turning down the dead key.

Turboomni
02-10-2020, 01:14 PM
Yes I know you do this but I guess there are a lot of guys that have plugged their tweaked radios into a amp and splattered everyone in the area before their amp blew up .

whiteastro
02-10-2020, 04:51 PM
Yes I know you do this but I guess there are a lot of guys that have plugged their tweaked radios into a amp and splattered everyone in the area before their amp blew up .

Yes I laugh because some people do not follow the instructions. You might say they could screw up a 1 car funeral. LOL If you check out that filter number in my first post they claim that filter # 27/586 is suppose to handle 300 watts AM and 500 watts SSB. That is more than any of my RM Italy amps will put out. PS. I don't have any radios that have been Peeked & Tweaked. I'm beginning to think that all I would have done is to check them for alignment & modulation. I don't have enough faith in my local guy because he has no real training just friends on the radio that guild him. He's learning as he goes and does alright for small stuff!

JesseJamesDallas
02-10-2020, 05:59 PM
Thanks for the comeback JJD you said something I feared ( Less Watts ) and I will be watching close for that problem. I bought 3 because I have a KL200P a KL203P, and a KL300P. The KL 200P & KL203P are for my car and van. The KL300P is for my radio bench. I live in small town with a lot of neighbors and I don't want to give them more to bitch about! ( And they Do ) I might have to save my Palomar 300A for my future country home. The other day I was playing with my Palomar on AM Channel 19 and I had a trucker comment on how he thought I was going to blow the windows out of his truck. Makes you wonder about these Old cheap neighbors and their Old TVs running a digital converter box I don't need the FCC knocking on my door if you know what I mean! They ( Filters ) didn't cost that much so if I end up not using them I'll put them with my other mountain of electronic junk LOL out for the yard sale! PS If they cut some of the noise in my radios that wouldn't hurt my feelings either!
I doubt your going to have any problems with the neighbors running those amps with/ or without the filters...It's not like it was back 30-40 years ago when just a stock CB Radio could mess up a TV set...since just about everything now has gone digital, CB's and amps don't hardly mess with anything...

-=UNLESS=->>>>You have a radio that's had several golden screwdrivers stuck in the back of it to squeeze out every last drop of watts the radio is capable of squirting out! That's where you run into problems is with radios that splatter all over the place...Run a splatter-box radio into a amp, and harmonics will be flying everywhere and getting into everything...

That 300A you have shouldn't bother anything either...Those guys saying your about to blow their windows out, are just complimenting you on how well your radio sounds is all...

I talk on my Cobra 2000 that's hooked to a 300A, with my TV on, and the computer all at the sametime and the radio and amp doesn't get into anything...and the TV is less than 15' away, and the computer's monitor is actually sitting on top of my Cobra 2000!

Another thing! I have a RCI 2980wx sitting next to the Cobra, it has it's own amp, a XForce 1x4 base amp, which is sitting literally "side-by-side" next to my computer and there's no affects there either!

bottom line...don't worry about ol' Uncle Charlie....
https://i.imgur.com/w4WjctB.jpg

whiteastro
02-10-2020, 06:30 PM
I doubt your going to have any problems with the neighbors running those amps with/ or without the filters...It's not like it was back 30-40 years ago when just a stock CB Radio could mess up a TV set...since just about everything now has gone digital, CB's and amps don't hardly mess with anything...

-=UNLESS=->>>>You have a radio that's had several golden screwdrivers stuck in the back of it to squeeze out every last drop of watts the radio is capable of squirting out! That's where you run into problems is with radios that splatter all over the place...Run a splatter-box radio into a amp, and harmonics will be flying everywhere and getting into everything...

That 300A you have shouldn't bother anything either...Those guys saying your about to blow their windows out, are just complimenting you on how well your radio sounds is all...

I talk on my Cobra 2000 that's hooked to a 300A, with my TV on, and the computer all at the sametime and the radio and amp doesn't get into anything...and the TV is less than 15' away, and the computer's monitor is actually sitting on top of my Cobra 2000!

Another thing! I have a RCI 2980wx sitting next to the Cobra, it has it's own amp, a XForce 1x4 base amp, which is sitting literally "side-by-side" next to my computer and there's no affects there either!

bottom line...don't worry about ol' Uncle Charlie....
https://i.imgur.com/w4WjctB.jpg


Thank JJD for the vote of confidence! LOL

mjd420nova
02-11-2020, 02:06 PM
Rack'em and stack'em. I used three separate filters, a low-pass filter on the output of the radio (loss of -.2 db) and the amplifier. The other two were on the output of the amplifier, one of which was a five band adjustable filter. All were installed, and the band adjustments made with the help of a spectrum analyzer. This was done with 100 watts, AM, on 27.495 into a dummy load. Then the final stage of the 100 watt amp was adjusted for the cleanest signal with as much of the harmonics tuned out. It can get complicated, tuning each stage, checking the SWR at each point to insure a clean signal to the final stage. It is important to stress that like lightning arrestors, surge suppressors, wall outlets and power supplies are properly grounded. Without a proper ground to the filter, the "bad stuff" gets filtered to the outside of the coax, radiating even more. I was able operate an AM/SSB station in a huge metro area where TV CH 3 was in use and I didn't interfere with my own TV. Clean signals are the gold standard.

whiteastro
02-11-2020, 03:19 PM
Rack'em and stack'em. I used three separate filters, a low-pass filter on the output of the radio (loss of -.2 db) and the amplifier. The other two were on the output of the amplifier, one of which was a five band adjustable filter. All were installed, and the band adjustments made with the help of a spectrum analyzer. This was done with 100 watts, AM, on 27.495 into a dummy load. Then the final stage of the 100 watt amp was adjusted for the cleanest signal with as much of the harmonics tuned out. It can get complicated, tuning each stage, checking the SWR at each point to insure a clean signal to the final stage. It is important to stress that like lightning arrestors, surge suppressors, wall outlets and power supplies are properly grounded. Without a proper ground to the filter, the "bad stuff" gets filtered to the outside of the coax, radiating even more. I was able operate an AM/SSB station in a huge metro area where TV CH 3 was in use and I didn't interfere with my own TV. Clean signals are the gold standard.


Thanks for the info! Just like any field you go into it can get very technical and requires a lot of study. I was a licensed Waste water treatment plant operator and was required to do constant study to keep my license active. The chemistry and math was staggering. I was a certified welder at one time and there is a lot more to welding than people realize. The USAF taught me to be a AirFrame Repairman which can get technical. I'm glad I'm finally retired and can shift into Neutral! LOL

JesseJamesDallas
02-11-2020, 04:24 PM
Rack'em and stack'em. I used three separate filters, a low-pass filter on the output of the radio (loss of -.2 db) and the amplifier. The other two were on the output of the amplifier, one of which was a five band adjustable filter. All were installed, and the band adjustments made with the help of a spectrum analyzer. This was done with 100 watts, AM, on 27.495 into a dummy load. Then the final stage of the 100 watt amp was adjusted for the cleanest signal with as much of the harmonics tuned out. It can get complicated, tuning each stage, checking the SWR at each point to insure a clean signal to the final stage. It is important to stress that like lightning arrestors, surge suppressors, wall outlets and power supplies are properly grounded. Without a proper ground to the filter, the "bad stuff" gets filtered to the outside of the coax, radiating even more. I was able operate an AM/SSB station in a huge metro area where TV CH 3 was in use and I didn't interfere with my own TV. Clean signals are the gold standard.
Just wondering..."when did you have this set-up?"

whiteastro
02-12-2020, 08:07 AM
2400 This is RM Italy's instructions for the filter between the antenna and amp.

mjd420nova
02-12-2020, 06:14 PM
Was in use from 1974 until 2016. As a field service engineer, with military electronics experience with radio transmitters and antennas, radar and passive and active ECM. A spectrum analyzer is the best tool for locating and eliminating interference signals. Harmonics are a big part of what needs to be filtered out but a good clean main emission goes a long ways to reduce interference.

whiteastro
02-12-2020, 07:01 PM
Was in use from 1974 until 2016. As a field service engineer, with military electronics experience with radio transmitters and antennas, radar and passive and active ECM. A spectrum analyzer is the best tool for locating and eliminating interference signals. Harmonics are a big part of what needs to be filtered out but a good clean main emission goes a long ways to reduce interference.


I'm sure you know your stuff and it is all over my head! LOL I've had no training in electronic just a interest! Thanks for the incite. PS. What do you think of RM Italy's instructions posted above?

JesseJamesDallas
02-12-2020, 08:53 PM
Was in use from 1974 until 2016. As a field service engineer, with military electronics experience with radio transmitters and antennas, radar and passive and active ECM. A spectrum analyzer is the best tool for locating and eliminating interference signals. Harmonics are a big part of what needs to be filtered out but a good clean main emission goes a long ways to reduce interference.
Figured you had that for the 70's...Bit different now days...With everything digital, you would have to be spitting out thousands of watts worth of harmonics to get into anything...

Plus electronics now days have better filtering than what was available 40-50 years ago...So far about the only thing I have ran across that my station got into was my daughters headphones...snap-on ferrite choke onto the cord took care of that problem tho.

I have more problems with my TV interfering with the radio, than the other way around...Damn Plasma TV's are noisy.