Problems with qrm

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Jacob Thomas:
When I'm on the radio, I have been having problems with qrm. I have a ft 920. I was kind of looking at the Inrad filters, but was also told by a ham on the air I would be better off saving up for a ft 1000 mk v. I don't really have that kind of money and am happy with the ft 920 excpet for this problem. I emailed George at inrad and he recommended a 2.8khz filter with a 2.1khz filter on their switchable board. I don't really have the money and was wondering if I'd be happy with just the 2.1khz filter. I had an ft 100d and noticed that the recieve from what I could tell was better on the ft 920, but I never really checked the selectivity. It seemed like the sound on the ft 100d was fine, but does seem fuller on the ft 920. I accredit that to having a better speaker for the ft 920. I was also looking at trying cw. I listened to it on 10 meter the other day and I'm interested in trying it. I have a straight key that I got at a hamfest for 10 dollars. Would that suit my purposes? What's the difference between the keys with the two paddles on them? And is the 2.4khz filter that is in the ft 920 going to be too wide for cw?
Jacob
73

James Benedict:
I believe a single filter of 2.1kHz would be an improvement, or a pair of selectable cascaded 2.1kHz filters would be even better (expensive). A FT-1000 MK V is not necessary. The FT-920 has a good blocking dynamic range of around 130dB.

Dee D. Flint:
The 2.1 filter will go a long way towards helping you out.  The audio won't sound as full naturally but when you have a station nearby it will attenuate it.

A straight key is fine for working CW.  Some people prefer them over the electronic keyers.  It's quite possible to get up over 20 wpm with a straight key if you so desire.

John:
Jacob,
You've asked good questions....and quite a handful as well....
The answers are NOT "absolute"....in that that there are variables that can mess up even the best solutions that you may get....
But here are some solutions.........

[First off the FT-920 is a fine rig, and there's NO reason to get rid of it!!!!!
Possibly the "..ham on the air..." that told you you'd be better off with a "Mark V" was just pulling your leg, or looking to get you to sell him your FT-920....
While the "Mark V" is a better rig,his advice is off base....]

NEXT.....
Be ABSOLUTELY SURE that you've got the noise blanker turned OFF!!!!   and then, also be SURE that you have the "pre-amp" (s) turned OFF!!!!!!!!!!
If either of these was "ON", you may find that I've just solved 90% of your troubles......

Also, remember that during a "contest weekend", like this weekend with the CQ WW DX Contest (phone), you'll find quite a bit of QRM since there are simply more hams on the air.......


{I'll give you a quick, short answer up front...and then more details/solutions below...}

[You will probably not notice a "significant" difference in your FT-920's qrm rejection ability going from a 2.4khz filter to a 2.1khz filter.....
Although the InRad filters have a reputation of being better and a with a bit sharper skirts than the "stock" filters, the key to this answer is the word, "significant".......it depends on the details of your qrm situations (band, mode, antennas, FT-920 control settings, contest weekends, etc. etc.....) and of course your personal tastes....]


Now onto the details....

The first three things to examine are:
1) Antennas,
2) Operator skills,
3) "Luck"....(also including understanding propagation, etc.)

(and then you can look at filters, etc.....)

1) Antennas can be your BEST way to reduce QRM....
{The ultimate desire in all communications is to improve the S/N (signal to noise ratio).....or S/I (signal to interference ratio)......
As with any mathematical fraction you can increase its valuve by INCREASING the numerator (the "signal") of DECREASING the denominator (the "noise" or "interference".......
Or the ultimate is doing BOTH!!!!!}
Using a directional antenna can be the BEST way to reduce QRM.....note that "directional" is usually understood to mean "azimithinal" (compass bearing), But should also be understood to encomapss the antenna's radiation angle as well......

Depending on,
 A) what band(s) you're experiencing QRM on,
 B) what locations, or areas the QRM is coming from,
 C) how "strong" and/or pervasive the QRM is....
you may be able to erect a simple antenna that can
"null" the QRM, and/or "peak" the desired signal!!!!!
While many hams use the "pointing the beam in your direction" approach, to fight QRM, the antenna (yagi, etc) can be used more effectively by pointing the "null" (typically off the side of a yagi) at the location(s) the QRM is coming from....

You can also use an antenna with a VERY low angle of radiation (great for DX) to reduce the strengths of more local signals, such as those within 1000 miles or so.....(this is a VERY efective "QRM filter" on the low bands, especially 75m and 40m where the night-time "locals" can be VERY strong.....)
You may also consider an antenna with a high angle of radiation, if you're looking to work more "local" and find signals from across the country (or across the world) are causing some QRM.....


2) Operator skills and using the features of your rig properly can be VERY effective to fighting QRM.....

Simply checking to see who is around you by +/- 5khz (called "situational awareness") and deciding what frequency might be a better choice for your QSO, or CQ, etc....
(How much do we ALL wish that the guys running NETS would do this!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!)
Sometimes it's as easy as fitting inbetween two other QSO's.....NOT too close to either......
Sometimes it's NOT easy at all!!!!  Hi, hi....

Using your ears is the best way to fight QRM....
That means, listen (and listen a LOT) BEFORE you decide to use any particular frequency....

Also using your rig's features (as well as your antennas, your "skills", and your ears) properly can be of help when fighting QRM.....
A simple twist of the "Passband Tuning" or "IF Shift",
when you've got some QRM close by, can really help out....

If you've not spent a hour or two reading the FT-920's
manual, and at the same time, twisting some knobs on the radio while LISTENING to what the happens to the signals when doing this, then you NEED To do that NOW!!
BEFORE you spend one dime on any filter, antenna, etc...
{When doing this, unplug your microphone / cw key, and put them in a drawer across the room (or in another room), as this will reduce the "temptation" to start talking with someone when you're supposed to be "learning"......}
When you've "finished class", then get on the air with someone....(answer a CQ, etc.) and try out what you've learned while talking with them.....and you may wish to include them in what you're experiemnting with, just be careful, as you may get more advice than you wish for, and a lot of it might be useless....

3) "Luck".....
Don't laugh, "luck" can have a lot to do with this....
What some call "luck" others call "skill"....
I believe a little of both come to play here!!!!
Understand radio propagation and how antennas can be used to effect your signal, AND your receiver S/N or S/I......

Please read up on this in, "The ARRL Handbook", "The ARRL Antenna Book", and "ON4UN's Low Band DX'ing"....
All 3 of these books are GREAT.....
But, I assume that you already have a copy of "The ARRL Handbook", since without it you'd be lost....and at the mercy of all those "sales/marketing people", etc....


AND, getting back to your question about "filters"....
George at InRad is a great resource, and I don't wish to second guess him, but if you really NEED a narrower
filter, why not try a 1.8khz Filter......It will surely affect the "fidelity" and audio characteristics of your receiver...but should be "narrow enough" to allow a noticable (or significant) "capability" to reduce QRM.....BUT you, the operator, still will need to know how to use your new filter (and your rig's other features) properly.....

///////////////////////////////////////////////////////

...looking at trying cw....would a staright key suit your purpose?????

Probably, yes......BUT, you may find a "straight key" to not be to your liking......and may wish to try a "keyer and paddles".....
Although, a LOT of this is personal preference AND a LOT more comes with experience....you might just need to try it and see.....

 The FT-920 has a built-in keyer....that's the thing that those "keys with two paddles on them" work with....they're known as "Iambic Keys" or "Iambic Paddles".....
AND, they NEED to be attached to a "cw keyer" to work....and they do work very well......
When you push on one paddle you get "dahs", and when you push on the other you get "dits".....
So simply "squezzeing" the paddles between your thumb and index finger, and placing the pressure (or moving your thumb and finger) properly you get to make CW characters with perfect "weight", etc...

///////////////////////////////////////////////////////

As for whether a 2.4khz filter will be too wide for cw?????
The answer is:  Usually, YES.......
If the band is "quiet" and NOT crowded, then you'll find the 2.4khz filter to be adequate for casual cw operations......
BUT, when the band is hot, and crowded, you'll certainly find a "narrow cw filter" to be almost an absolute necesssity!!!!
Typically a 500hz filter is most useful for "most cw operations.....But cw dx'ing, cw contesting, etc. will usually necessitate even a narrower filter (200hz - 250hz)
BUT, ALL of that can wait untill you've mastered all of the above....(especially understanding radio propagation AND understanding the proper use of all of your rig's features.....

I wish you good luck....and I can't stress enough the importance of "skill" in fighting QRM.....
Knowing what to do is MUCH MORE important than just having "a narrow filter"....
Knowing exactly how your rig performs (NOT always how the manual says it will) is VERY important!!!!!! That's why I mentioned right up top, to make sure that your noise blanker and RX pre-amp(s) are OFF, since they can be adding to the problem, or even the total cause of the problem depending on the situation....

73,
John,   KA4WJA




Jacob Thomas:
I read the manual and understand propagation. I can't put up a beam because I just don't have the room. My house is on a 30x100 foot lot. There isn't that much room for the WindomHSQ I put up now. Although it's not supposed to, I have it setup as an inverted v right at the moment. Because of the low height and inverted pattern, I have rf in the shack on 75 meters. It says in the antenna handbook that Windoms have rf problems anyways. My first step is putting it up correctly and adding some ferrite beads. Grounding didn't seem to help me any, but I think it's mainly because I'm up on the second story with my hf rig. The rf isn't that bad now, but used to be real bad. Like one ham told me, don't talk on it when the swr is higher than 2:1, which seems to be good advice.
As far as the qrm problem I'm having, it's mainly on 7261 listening to the 1721 group. I've missed my turn and gave up a few times now because I can't hear people because of the qrm. I did read the manual and playing with the controls and knowing what they do really helps. I always use the dxp and filter out all the static. It sounds kind of weird at first, but to me it actually sounds more pleasant for long periods of using the radio. I pretty much never use the preamp and almost always have the attenuator on. I never seem to have a problem hearing people, my only problem is the qrm. Like the manual says, the shift seems to help some too.
Basically what I'm getting is just to keep my money and live with it. From what you said, buying the 2.1khz filter wouldn't be worth the money, time, and effort. I think that 1.8khz would be a little narrow for me. I've never found alot of cw going on. I find some here and there now and then. When I first got the radio, I would hear cw, and it would fade away. I had read the manual, but forgot about the part to turn off the notch filter. The second time I read the manual, I remembered and had to laugh at myself. Anyways, I guess I was hoping for a miracle or something with the inrad filters. I was hoping it would cut it down enough to make out what they are saying.
I'm going to see if I can borrow a paddle from a nearby ham. I'm sure someone in our club has to have one. I'll ask at our next meeting.
Thanks for the responses.
Jacob
73

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