Icom IC718 - Noise, Help Needed

Discussion in 'General Technical Questions and Answers' started by M7OJW, Dec 3, 2019 at 12:27 AM.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: L-MFJ
ad: MessiPaoloni-1
ad: Subscribe
ad: Left-3
  1. M7OJW

    M7OJW Ham Member QRZ Page

    Hello,

    I am a relatively new ham (licensed in February of this year). I have been trying, since February to get my first HF station up and running, but am finding it so frustrating, nearly at the point of giving up.

    The noise level I'm experiencing is s9++ on most HF bands, it's very hard to hear anyone at all, I am yet to manage to make a contact (despite trying very hard).

    My setup is as follows:-

    IC718
    MFJ 993
    OCFD 40-6m 4:1 balun in inverted V configuration with balun approx 20ft above ground
    RG213 coax feeder

    The rig does not have the DSP unit or any extra filters in. I'm reluctant to invest in any of these without knowing if they will help.

    I'm beginning to wonder if there's something wrong with the rig, I can pick up broadcast stations and very few hams and at that very poor signals.

    I'm going to try some chokes in the feedline next, but like I'll admit I'm inexperienced and not made of money, so can't afford to throw more and more money at things that may not help.

    Is it possible the rig is faulty? Or am I just in an area where noise is a massive problem? Would help to try another rig through my antenna etc, but promises from fellow club members not fulfilled and to be honest I've given up on going to the club really now. I realise nobody is obliged to help me, but I thought maybe that was the point of a club, nevermind.

    Any suggestions would be much appreciated as I'm starting to wonder if I should just forget about HF and stick to VHF/UHF, at least it seems to work.

    Anyway thanks in advance,

    Cheers


    O
     
  2. N7EKU

    N7EKU Ham Member QRZ Page

    Hi Owen,

    I doubt there is anything wrong with your rig. High noise from the RFI from all the modern electronic equipment that we are surrounded with is a problem we all have to deal with.

    Your problem is a bit compounded with your set up. An OCFD is prone to common mode current, and thus noise pickup, on the shield of the coax.

    On setting up a station, most of us need to do some RFI investigation for our own household first. This is best done by running the rig on a battery and turning on the house circuits each in turn to see if some appliance or house fixture is causing noise. You can also just try unplugging things while listening on the radio to see if some particular item is causing a lot of noise.

    Noise can also come from things at the neighbors or in the neighborhood. Which are a bit harder to pinpoint and solve (so it's better to start on your own place first. You can also try listening at different times of the day to see if the high noise varies. Battery chargers, plasma TV's, and grow lights seem to be the number one noise generators that can cover a lot of distance.

    Having the antenna very close to the house can cause more noise pick up too. Up and away from any house is best.

    You might try errecting just a single band dipole having a current choke on the coax. This can be as simple as coiling extra coax around a 4-6" plastic pipe a dozen turns or so. An antenna like this will have less noise pickup on the coax and should be quieter.

    Hope this helps,

    73,


    Mark.
     
  3. M7OJW

    M7OJW Ham Member QRZ Page


    Thanks Mark,

    I have some drainpipe I liberated from a skip (dumpster?? think that's what you guys call it) the other day, so will try putting a choke on the coax. I was looking at a T2FD antenna as I've read they are good from a noise perspective, but have also read a lot of the RF is dissipated as heat which saps the TX power. I guess I should try single band dipole for say the 20m band first as you suggest. If this helps with my problem, would making a fan dipole be a good idea? I don't think I can fit 80m into my garden anyway, but I could fit the mains bands from 40m upwards. Is 20ft high enough of the ground would you say? Does the inverted V formation make the antenna more susceptible to noise than a flat formation?

    All advise is much appreciated, I really don't want to give up on HF, I guess maybe my expectations were a bit high to start with.

    Cheers mate

    73

    Owen
     
  4. M7OJW

    M7OJW Ham Member QRZ Page

    Forgot to ask should I make the dipole with a 1:1 balun and feed with coax, or is ladder line better for the feeder?
     
  5. N8FVJ

    N8FVJ Ham Member QRZ Page

    You wont believe how much noise an AM COM ClearSpeech speaker can remove from the bands. It is as good as any DSP I used in modern radios. At $239 it is expensive, so buy used for about $110. It will take you from difficult copy to armchair copy.
     
  6. AI3V

    AI3V Ham Member QRZ Page

    Can you operate portable?

    Something a simple as a center fed halfwave dipole (coax feedline) at a park out in the country away from houses and powerlines?

    For quiet on hf you need to get away from "civilization" :)

    Rege
     
  7. M7OJW

    M7OJW Ham Member QRZ Page

    Might be the best option, I have a spare car battery I could run the IC718 and tuner off of, so could put it in the car and string up an antenna at a picnic site or similar and see if I have any luck there. If it works well, maybe I should get a more portable rig e.g. ft857 or something?
     
  8. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    If you haven't yet, try listening with the pre-amp off on 80 and 40m. You shouldn't really need it with a full-size antenna on those bands. Front-end noise will actually cover up weak signals on those bands with the pre-amp on and hooked up to a full-size antenna!

    When working DX on 40m CW with a full-wave delta, I not only have the pre-amp turned off, I turn the RF gain down some. Doing so causes weaker noise signals, like distant lightning crashes and far-off electric fences, to "pop in" seemingly out of nowhere. It works the same for weak desired signals, too. The IC 718 has plenty of gain but does not seem to have the best dynamic range in the world.

    On 20m and up, even with a full-size antenna, you can begin to use the pre-amp.
     
  9. N7EKU

    N7EKU Ham Member QRZ Page

    Cheers Owen,

    The former is better as routing coax is a lot easier and it mtches the feed point impedance of the antenna so you won't need to use a tuner for a large part of the band.

    At 3/8 wavelength and higher, a dipole will start to show a directional pattern and lower angle on receive and transmit so better for DX. Lower will make it a more omnidirectional and local coverage antenna. Of course longer contacts could still be made when the band is good. Inverted V doesn't increase noise pickup, it just makes the pattern more omnidirectional among other things.

    The T2FD has a reputation for low noise just because it's a lossy antenna. Turning down the RF gain control or using the attenuator accomplishes the same thing.

    A fan dipole is fine. Or you can use traps like from sotabeams.uk to make a combined 20m 40m e.g.

    73

    Mark
     
  10. N7EKU

    N7EKU Ham Member QRZ Page

    PS: The sotabeams site has lots of good ideas about portable operation :)
     

Share This Page

ad: qroparts