Amazing Results With QRM Eliminator

[johnkyrle]

I have looked just now for the X phase kit but apart from a German electronics site which,when you add it all up,turns out quite expensive.Anyone any ideas?

[ghost123uk]

The noise antenna has to feed what it picks up to the electronics in the eliminator. The eliminator then subtracts it from what the main antenna picks up, leaving you with less qrm noise going to the transceiver.

[MrWeetabix]

So, another holy thread resurrection Batman...

Just bought one of these...

2699DFE4-5107-447D-81AC-F459DA3F1508.jpeg

... it was my understanding that it was auto-sensing for TX, but now I am not sure

Anyone used a similar type and can advise? The ‘documentation’ isn’t worded particularly well to determine if it is indeed auto sensing or not. What further confused the situation further was the fact it came with a PTT socket on the back and a RCA cable to wire to the radio...

[Otter]

Mine isn't that exact one - mine came from Russia - but the schematic shows RF sensing or if you use the RCA it should earth on Tx.

[MrWeetabix]

I will do some more digging then. Hoping its sensing as I want to be able to use it with my new 11m radio rather than just the HF set.

[Buick Mackane]

I personally wouldn't take the risk craig. The MFJ Version is meant to be auto sensing. But the manual advises against using it Plug it in to the radio via the CAT port would be my advice.

My results with these turned out to be not so good as i originally thought as the QRM Came back. Lots of videos on youtube showing them performing miracles. I'm not covinced. I think they do reduce QRM but also reduce received signal strength too. Bit like an RF Gain control.

[MrWeetabix]

Initial testing seems negligible, but 11m was dead at the time. Need to find two stations a decent chuck away to test it with. I have PLT between 27.480 and 27.850 which whilst its only s3-5 I was hoping to get down some. The unit does seem to do this on RX but without an actual station on there its hard to judge if it is working as advertised or as you say more like an RF Gain :-/

[Buick Mackane]

Apparently the key is getting the noise antenna right so it picks up only the noise and not the actual signal your trying to receive. Like i said above i'm not convinced despite the name of this thread. Turns out the actual QRM i was receiving wasn't present the day i played with the eliminator which made me think the eliminator had worked wonders.

Keep us posted on your results with it craig

[ghost123uk]

I had the MFJ one.

Despite spending hours experimenting with different "sensing" aerials and different aerial locations, I found it made no useful difference
I sold it on Ebay.

I contacted the original guy I bought it from, explaining I was in no way complaining about the sale (I had left him good feedback re condition and speed of posting etc) but asking how he got on with it (kinda "why did you sell it"?) and he said he sold it for the same reason, and he was a licensed amateur.

After the guy I sold it to had left me good feedback, I contacted him. He said he was suffering from interference from a neighbours Plasma TV as it only started in the early evening, and disappeared around 11:30pm. He said it was working very well for him.

So the message seems to be that they (well at least the MFJ one) is good at nulling out a specific local source of interference, but no good for a general "mush" of QRM. When you consider the way they work, this does make sense.

[MrWeetabix]

Thats all good info. I think the QRM I have is PLT on certain bands.... From using a very small antenna as the noise antenna in the shack I can get the noise down by a few s-points, but there’s been a lack of QSOs locally for me to really asses if its actually lowered the noise and not just the overall RX.

I think I will run some RG58 round to under the vertical and run a vertical length of wire as the noise antenna, so hopefully it sees the plt too. The unit cost me about £55 delivered and seems to be very well built and to a professional finish, so lets see of the gubbins inside matches that finish

Thanks for all input, greatly appreciated

[MrWeetabix]

Short video of the apparent reduction, though I really need two stations on ssb to listen to test

[MrWeetabix]

I asked the seller to clarify the wording of the listing, with regards to if the device is auto-sensing and doesnt need the send connection from the radio, as most cbs dont have this and they specifically say it works with CBs. I also asked for the manual as there wasnt one in the box

He replied thanks for your question and sent me this...

F45C3F6A-9F3D-4220-81C5-1A6ECB527A56.jpeg

So side-stepped the question about then CB then apparently sent me some old crap he found on google.

The plot thickens....

[MrWeetabix]

He just replied regarding the ptt with a CB

“ hello my friend
thanks for your email
If there is no PTT connected, only receive
It cannot be launched. Once launched, the internal circuit will be burned.
have a good day !”

I have suggested he remove the reference to CB as this is misleading. You need a PTT to switch out the device on transmit or its Burn City for you. I am pleased I approached this with an abundance of caution, I wont how many have not

I have seen some people have developed their own PTT interfaces which work with their own specific CBs, but this looks to be a fairly complex for most users.

Just remember, these types of devices DONT WORK with CB Type radios!

[Raverrst]

I do read some have auto sensing, do any eBay units come with this? As I run afew radios so would need something universal..

[MrWeetabix]

I do read some have auto sensing, do any eBay units come with this? As I run few radios so would need something universal..

I'd make sure you ask the specific question of the seller before you buy. Some of the Chinese sellers don't really tell the full story in the item description.

Another point of note, also mentioned on this thread is that even the bigger brands such as MFJ have auto-sensing inbuilt, but in their own documentation they recommend not relying on this as its more intended as a fail safe, should you forget to connect the PTT or it becomes disconnected somehow.

Personally, looks like I'll continue to play with this device on HF with a HF Radio, but the PLT I suffer only really affects 11m, so I may well end up selling it on :-/