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Reviews For: RF Inquiry

Category: Filters, RF: bandpass, duplexer, lowpass, highpass, RFI/EMI

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Review Summary For : RF Inquiry
Reviews: 5MSRP: 210.95
Low-pass/Common-mode filter
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
KA3DPW Rating: 2007-11-02
Interference Be Gone!! Time Owned: more than 12 months.
I have the 250 watt model between my Kenwood TS-830S transiever and my Yaesu FL-2100B linear with a Kenwood LF-30A harmonic filter.

I have the 500 watt model and another Kenwood LF-30A between the output of the linear and the MFJ Versa Tuner V

This filter system sits on top of a 3 inch copper strap upon which the harmonic filters are tighly screwed down to upon my bench in the back.

The length of the total bus is about 7 foot to the 8 foot ground rod and everything is attached in between.

I'm so close to my neighbors hee that I can look out my window and see into thier windows.

I run full power on any band on my full size 40 meter quarter wave with 60 radials fed with 1/2 inch hardline buried in the ground, on any band and nobody hears a thing.

Better yet they can't see my vertical. It's painted flat black, Out of Sight-- out of Mind. They've even come over and helped me put my antenna up.

They're impressed with me since they can use thier stuff without hearing anything from me. I get to run as much power as I need and I can keep a good clean signal.

I run SSB and CW. I don't have AM, so I can't try that. But I bet it would help there too.

I've had just harmonic filters and still got into TV's and radios and a computer. Now I can run power and not even bother the electronics in our own house.

All the other tricks helped alot, but these common mode filters added seemed to break the rest of the ground loop.

I find even in the station interference isn't a problem. I thought for sure I'd need quarter-wave traps, but so far over the last couple years I haven't had a problem.

The station I moved out of the house to a separate out building and it's even closer to the neighbors and still I have no problems.

I recomend these ideas to any ham who wants to be free of the problems with others. I definitely recomend these filters.

I had a little bit of trouble before despite all other things helped alot, but these filters really put the kabash on the last of it.

Now I hear weak signals I could never hear in the house and have a clean signal that gets good ratings from other stations with a minimum of line loss.

I definitely recomend these filters. But you won't find them at AES anymore for some reason. You may need to look around.

Use good transmission line with the most amount of braid you can get your hands on or better yet get hardline. Ground your harmonic filters well and keep your total distances as short as possible to ground and don't let the station float above ground.

These things go along way toward your RF freedom. The insertion loss of these filters and harmonic filters is so small you won't need to worry about the insertion loss at HF.

These things break the stubborn ground loops you may not break using the other ways. But they all work together.

Take the time to find these things and use a flat stock for your path to ground. I use 3 inch copper strap all the way. Of course I do have alot of power to use too.

Try it, I definitely recomend it. It worked for me who can look inside the next building of a few neighbors and still no problems anywhere.

It'll break those ground loops, isolating equipment from each other inimizing the problem. A good ground is not to be understated. Don't use a polluted ground like cable TV or your power service.

Now if I can just break the interference from the local broadcast station.
VR2XMQ Rating: 2007-03-30
Best of the best! Time Owned: more than 12 months.
Want top notch engineering and build quality with high performance specs. to match? The you cannot go wrong with the RF Inquiry Hi-Q Common mode filters. I use these plus other filters made by this firm and the quality is outstanding.

You get what you pay for, quality and performance does not come cheap.

Great responsive company, I usual;y get same day reply from this Company in JA.

73 Steve, VR2XMQ
WB6Q Rating: 2004-12-10
Little known Gem Time Owned: more than 12 months.
I own both the 5Kw and 250w filters. Read the review of KD9WIS I could not day it any better. If every ham had one in the line there would be no TVI, BCI, hi fi or telephone interference because it would be all gone with these filters. Every ham should be using one. They are available at AES, my advice rush out and buy one.
K5UJ Rating: 2002-02-07
Okay, but a little overpriced Time Owned: 3 to 6 months.
The RF Inquiry line of common mode coaxial cable isolators seem to be effective and well made (I am using the 5 kw model). There are two available: one rated at 250 w. and the other at 5 kw. They sell for about $90 and $125 respectively. Both models are housed in PVC pipe with end caps and SO-239 UHF connections. These filters are used to attenuate RF travelling on the feedline shield they are connected to. It might be RF coming back from an antenna or moving in a ground loop between for example, your transmitter, transmatch, ground bus and back to your transmitter again. These filters interrupt these loops and help keep RF off of feedlines and house wiring safety grounds where it can go where it is not wanted. Mine seems to do a good job--I gave it a 4 only because of its price however I admit that I may have paid for a 5 kw handling ability which I did not need. N.B. Radio Works sells an isolator for about $35 that handles 2 kw.
If you buy a common mode filter, don't throw out your low pass filter. You may continue to need it in series with the c.m unit (place it between your transmitter and the c.m. filter) because the two perform different functions. The c.m. filter is not a low pass filter. If you operate with a linear, you will need two c.m filters: one between your exciter and linear and the other between your amp and antenna, in order to break up all the loops that might form between your gnd. bus, exciter, linear and other grounded accessories (transmatch, coax switch...) inserted in your feed. For more information go to
KB9WIS Rating: 2001-10-05
Finally a low-pass filter that works!! Time Owned: 0 to 3 months.
I've tried various low-pass filters with my HF rigs.. and I could never prevent neigbor TVI! I've tried properly grounding all equipment and antennas, and almost every low-pass filter there was available.. Nothing seemed to work!! However, that was the past. I recently ordered one of these "Common-mode" flters from AES, and I've never had a problem again!! I live in the city, with alot of close neighbors, and this filter has cured over 90% of my current problems. I only wish they would of thought of this filter sooner.