Results 1 to 4 of 4

Thread: Beginner question on reception of SW / HF

  1. #1

    Default Beginner question on reception of SW / HF

    Hi,

    I am still somewhat a 'nubie'. I have various cheap radios such as a v115 (https://www.amazon.com/Retekess-Port.../dp/B01ARN28SQ) and a couple of TECSUNs (https://www.amazon.co.uk/Tecsun-PL-6.../dp/B004Q21I4U) and am trying to receive wefax and CW which I wish to pipe into software of various kinds. I am in a built up area but have almost no sucess in receiving such signals. These are received not so far away on web based SDRs. I have tried various Ariel enhancers such as the extended ariel that comes with the PL-606 and ariel extenders (https://www.ebay.com/itm/Origin-TECS...FIQAvD_BwE:G:s) (yes I know this if for FM) but with no joy.

    Can anyone render any advise as to how to receive these signals at reasionable quality. I want to use small radios and not more bulky ones as I wish to do this mobile, specifically but not exclusivly at Sea.

  2. #2
    Super Moderator 5B4AJB's Avatar
    Join Date
    Mar 2008
    Location
    Meneou, Cyprus
    Posts
    2,179

    Default

    I had a lot of success with a simple long wire, an ATU also helped to some extent. WeFAX doesn't require a huge signal to noise ratio, but, the images will come out better on a proper tuned antenna.

    Living in a built-up area usually means quite high ambient radio noise levels, especially at H.F., where you want to listen. Try and make sure your D.C. to the radio is as clean as you can get it.
    Tune to a signal on your normal setup, then switch the radios power source to a battery or battery pack (even AA's will work for testing) compare the resulting noise and see!

    Using a preamplifier with a noisy signal will only increase the noise level. It may be well worth you building a antenna for a single station that has a very narrow bandwidth.

    A magnetic loop (here it comes) has an extremely narrow tuned resonance and is great for noisy locations, easy and cheap to make too...

  3. #3

    Default

    Quote Originally Posted by 5B4AJB View Post
    I had a lot of success with a simple long wire, an ATU also helped to some extent. WeFAX doesn't require a huge signal to noise ratio, but, the images will come out better on a proper tuned antenna.

    Living in a built-up area usually means quite high ambient radio noise levels, especially at H.F., where you want to listen. Try and make sure your D.C. to the radio is as clean as you can get it.
    Tune to a signal on your normal setup, then switch the radios power source to a battery or battery pack (even AA's will work for testing) compare the resulting noise and see!

    Using a preamplifier with a noisy signal will only increase the noise level. It may be well worth you building a antenna for a single station that has a very narrow bandwidth.

    A magnetic loop (here it comes) has an extremely narrow tuned resonance and is great for noisy locations, easy and cheap to make too...
    Thanks, the environ is perhaps quite noisy. Lots of computers and tv around it. I have little space! The radios are already operating from AA batteries. Can you say more on the nagnetic loop?

    73

  4. #4
    Super Moderator 5B4AJB's Avatar
    Join Date
    Mar 2008
    Location
    Meneou, Cyprus
    Posts
    2,179

    Default

    Quote Originally Posted by 2e0sve View Post
    Can you say more...
    Its performance is similar to a dipole, that is, there are front & back broadside lobes of equal gain.

    Here's my 14MHz to about 50MHz magnetic loop.


    Pretty simple construction, there are many plans available on the web - look at a few before you begin. The main loop is aluminium usually, avoid steel as it is not much good at R.F. frequencies. You could even use a copper wire as the main loop, people tend to use this for top-band loops as they are so huge. The mounting mast must be insulated and is usually wooden or plastic tube with wood inside. The coax feedloop is 1/5 of the outer loop diameter, or thereabouts. RG213 is a good material for this as it will hold its shape (mostly) on its own. Search for "magnetic loop feed" or similar to see it's construction details.

    Tuning is done by remote, which is the most challenging part. The outer loop is split with a variable capacitor between it. You can manually tune it if you don't want to change frequency, but if you move frequency even a few kHz, you will need to re-tune it. I used a simple barbeque motor with a further speed reducer and a wire to a control at the shack. The capacitor can produce very high Voltages if you transmit through it.

    I cannot recommend this antenna highly enough for limited space or noisy environments, the only downside is you have to keep tuning every time you QSY...

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •