Tx Bandwidth

Interested to know what people find acceptable ? in terms of transmitted bandwidth.

I was challenged by the “Maritime Mobile” net on 20m this morning for causing adjacent channel interference (QRM). Apparently it is a “legal” - the term he used, operating practice to leave a 1 KHz channel space between stations. At best I would say a gentleman’s agreement here.

Needless to say I did check the frequency was clear and adjacent stations where suitably apart. I do believe 1 KHz is a tad excessive, unless the phase noise of his receivers LO was so poor it compromises the selectivity. Certainly not an issue here …

Not being a problem with PicAStar I QSY’ed down 1 KHz and reduced the Tx bandwidth down from 2.8 to 2.6 KHz in total width.

2.8 to my mind is not massively wide, whilst I do appreciate it is beneficial to run a smaller BW when DX’ing or trying anyway :wink: I would not have thought that 2.8 is excessive ! and yes it does transmit what it says.

Wonder if anybody else has had similar crowd control issues on 20m ?


Rarely not enough power :smile:
From what one has experience of One normally allows 3khz between stations
For if a station is being heard on say 7177khz I would op 3kz either side of that
out of respect

Band has been busy today for sure


You have an IL callsign and worse are technologically competent, that is the problem!

Except it’s not a real problem, it’s a problem for some who don’t think you have done enough to be on HF! Had you been using a G3/G4 call they would have been more circumspect about challenging you. My response would be to find a small PA, a pair of 8874’s say, and run some digital wideband tests next to them. It wont improve the way you will be treated on air but would put a smile on the faces of those who saw “net frequency police” get a touch of their own medicine.

If you run 10W as you claim in most posts, it matters not where you operate in relation to other stations, you wont be QRMing them. :slight_smile:

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20m is a busy band and efficient use of the available bandwidth rather than fidelity should be the key factor. Starting up 1kHz or less from an existing SSB net is not going to make you very popular.

If you were only 1kHz from him then you were too close, especially if you were below him. You say your bandwidth was about 2.8kHz, if so and you were 1kHz below him then 1.8kHz of your signal was over the top of him - not a polite thing to do. Remember that on USB your signal is all above your nominal frequency not centred on it.

Colin G8TMV

Guys, he said a 1 kHz channel SPACE, which should be more than adequate. The trouble is that the MM net is famously intolerant and act as if they own several kHz of the band. You often get complaints about them on the Zed and eHam from people who started up 5 kHz from them and got slagged off by them for potentially interfering with traffic. I’ve heard a theory that some of them are using a TRF receiver! :slight_smile:


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Making efficient use of BW - exactly not rag chewing in the upper portions of the band, I have ZERO whiskers on star - Its a brick wall on either side of the transmission and much effort has gone into achieving that with good opposite side band suppression. 1 KHz should be enough here IMHO it should not cause a problem.

Colin - I have not made it clear effective BW + 1 KHz spacing. You are taking my center display frequency rather then my skirt edge. By what you describe i would be practically on top of “it”.

Andy - Yes I felt exactly that, won’t be a problem after the 8th of December.


Thanks for the clarification. As described, a 1 kHz guard-band [Guard band - Wikipedia] should be more than adequate. Regarding efficient use of the spectrum I am talking purely from a technical perspective. As a general rule it is good practice to use the minimum bandwidth consistent with the mode of communication that you are using. It’s a matter of opinion whether the MM use of the spectrum is the best use.

Precisely Richard. I will edit my param’s to stick it at 2.4 Khz for 20m. It may make me sound like I am wearing tight trousers, but I probably fit in better ! Spectral power density is better I suppose if I am remembering the theory right.



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There is a fine balance to be achieved between optimum spectral bandwidth and intelligibility of course…

Lots and lots of papers on this subject.

One claims to run 10w is what one runs
Rig won’t put out any more strain strain poor old thing :smile:
Nope am one of the gen M3s that only run 10w

Good friend of mine serviced the radio couple months ago and said yep 10w across the bands she works on

TS120V trio

But with the mike surely if one over drive that surely that will bleed across the bandwidth a little its a Astatic road devil nice little mike works well.
One tends to try stay clear of freqs in use by at least 3kc not because one might cause them QRM more like other way around

Must admit like a bigger rig loads of power make is easier to get through some days but end of day one is licenced on 10W under my licensing conditions but one day when the tower and beam is finished will make it work harder for me

Go Go Go 10W :smile:

Better still next year set sights getting that 2E0 Licence

Hi Jonathan

If it’s any consolation to you I was challenged by 2 nets this morning whilst activating from Mynydd Cynros GW/MW-034. The first incident was with the Maritime Mobile net and I had been operating for 30 minute. I informed the station of the situation and asked for a callsign - none was given and was adamnat that I moved. I gave in as they were ‘loud’ and it was pointless continuing.

I found another frequency and operated quite happily for 15 minutes until another ‘loud’ station came in to inform me that they would be starting their net in a few minutes with pre-arranged skeds. I informed the station of my circumstances and that I had been operating on the frequency for some time - once again I was forced to move but not before I nipped in with a few more contacts with chasers and an s2s :smiley: My last contact was with Phil G4OBK who I think was wondering what was going on. I moved elsewhere but the damage had been done and the next move only produced a few chasers.

I could have held my ground but they would have drowned me out. Sad really but it did spoil my visit to 20m although today’s incidents are not common place on the majority of my activations.

73 de Allan GW4VPX

This happened twice to me today also Allan.
It is no good trying to stand your ground with these types - they just plough on anyway.

Ignorance that’s what it is!

ps. Does anybody know why my call sign on this reflector shows MW0IML
when I have changed it on both soawatch and data?

It was probably pulled over from SOTAwatch as MW0IML. If you want to change it you need to re-register. You can’t re-register with the same email address. Annoying but part of the spam fighting policies of this software. So change your email address and then accept the email you receive or your mail doesn’t change. Then register for a new account with your current email and I’ll approve you.

If you decide to remain a touch Celtic with the W in the call I’ll understand :wink:

10W is plenty of power.

73 Chris M0RSF

That is interesting Allan, so it wasnt just me. If the net does use those Marine vintage SSB transceivers then I can see why they are having issues with QRM.

Sailor I believe made them. Very primitive and simple no front end filtering. They really should use 17m instead, it would be far better for them.

I am not enjoying 20m SSB at all, going back to 17 and 15. Maybe the Key will yield more fun on 20m. Never liked the band.

5W is plenty ! Tom was booming in from The Cloud.


Agree Chris. In fact 5w seems plenty going off my results this morning. Then again my 100w from home never seems enough… :wink:

Your new here aren’t you? :smiley:

Nets own the frequency. They have special licences that actually state they can harass any non-net user off THEIR frequency. It doesn’t matter if you were there before for hours. It’s their frequency and they’re right to chase you off. Despite you thinking they could shuffle about a bit, it’s their frequency and only for them to use. What is amusing is when you hear them chase someone away and the net starts then 99% of the time they don’t have any traffic pertinent to the net’s purpose. They are normally just angry old men protecting their turf.

How to describe a net policeman… I know it rhymes with :anchor:


Brilliant Andy. New to using a rather impolite band in force YES !

Back to the pipe and slippers band. :smiley: