DCF 77 77.5KHZ

Useful information regarding antennas for SDR products.
Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

BBC London

Post by Mike2459 » Fri Jul 12, 2019 2:54 am

BBC London.JPG
BBC London.JPG (93.05 KiB) Viewed 3150 times

Reason: No reason

vk7jj
Posts: 206
Joined: Thu Mar 02, 2017 9:56 am
Location: Tasmania

Re: DCF 77 77.5KHZ

Post by vk7jj » Fri Jul 19, 2019 8:55 am

That's good work and deserves commending.

Here's what a large wide bandwidth loop can do; all the paths shown are for stations transmitting at 200 milliwatts or less and all were received in the last 24 hours.

Three receivers were running at once all connected to the one antenna.

The green 20m paths are stations received using an RSP1A. The amateur balloon in the Arctic was obviously up high enough to make the distance. Yellow is 40m and light green is 30m.

Phil
200mW rsp1A.png
200mW rsp1A.png (486.75 KiB) Viewed 3005 times

Reason: No reason

SDRguy22
Posts: 12
Joined: Fri Jul 19, 2019 4:34 pm

Re: DCF 77 77.5KHZ

Post by SDRguy22 » Fri Jul 19, 2019 5:01 pm

vk7jj wrote:That's good work and deserves commending.

Here's what a large wide bandwidth loop can do; all the paths shown are for stations transmitting at 200 milliwatts or less and all were received in the last 24 hours.
You are certainly getting excellent WSPR reception.

Bill
Last edited by SDRguy22 on Fri Jul 26, 2019 4:55 pm, edited 1 time in total.

Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: DCF 77 77.5KHZ

Post by Mike2459 » Fri Jul 19, 2019 6:40 pm

There is a gentleman from NZ on the NDB list who has received the carrier of DCF77 there. He must have a very quiet location to work from.

Reason: No reason

vk7jj
Posts: 206
Joined: Thu Mar 02, 2017 9:56 am
Location: Tasmania

Re: DCF 77 77.5KHZ

Post by vk7jj » Fri Jul 19, 2019 11:05 pm

Why doesn't DCF 77 use a miniwhip? What antennas does DCF 77 use?
Screen Shot 2019-07-20 at 8.45.06 am.png
Screen Shot 2019-07-20 at 8.45.06 am.png (368.11 KiB) Viewed 2925 times
If you made a whip just a bit longer than a miniwhip it would pick up a bit more of DCF 77's signal would it not?

And if you made it a bit longer still it would pick up a bit more, and so on. Antennas are so easy to make and so much fun they are the perfect complement for SDRplay products.

As an example of homebrewing an antenna for DCF 77 its Wikipedia page offers a suggestion
440px-Low_cost_DCF77_receiver.jpg
440px-Low_cost_DCF77_receiver.jpg (15.34 KiB) Viewed 2925 times
Don't get me wrong, if a miniwhip makes you happy then fine but it's another thing altogether to give people on this forum the idea that they have to go out and spend money on such a thing is not based on fact, they don't.

That is my motivation, to not just talk about this antenna or that because that never works out, people are too emotionally invested, so I'm trying to demonstrate beyond any doubt that with inexpensive wires and a bit of leg up, people who are crying out for antenna solutions on these pages can create something for themselves.

It's actually fun, I commend it to you :-)

Phil

Edit. the photo makes it hard to see the antenna which is said to be a complex T
Attachments
800px-T_antenna.svg-1.png
800px-T_antenna.svg-1.png (7.48 KiB) Viewed 2884 times

Reason: No reason

SDRguy22
Posts: 12
Joined: Fri Jul 19, 2019 4:34 pm

Re: DCF 77 77.5KHZ

Post by SDRguy22 » Sat Jul 20, 2019 12:49 am

Mike,

I find it interesting to read that you can receive signals from so far away on LF, which is a fairly noisy band, on such a low cost antenna. From what I understand you have designed an active antenna and I hope you can post a little more about it (some pictures and/or a schematic).

Bill
Last edited by SDRguy22 on Fri Jul 26, 2019 4:38 pm, edited 1 time in total.

Tech_Support
Posts: 497
Joined: Mon Jun 01, 2015 7:00 pm

Re: DCF 77 77.5KHZ

Post by Tech_Support » Sat Jul 20, 2019 5:54 pm

Gents,
These posts have drifted completely off topic to this thread. If you want to have such a discussion, please take it to private messages so as not to derail the original thread.

Thank you!!

Tech_Support

Reason: No reason

Tech_Support
Posts: 497
Joined: Mon Jun 01, 2015 7:00 pm

Re: DCF 77 77.5KHZ

Post by Tech_Support » Sat Jul 20, 2019 6:38 pm

This thread is now locked after a bunch of completely off topic posts. Sorry!

A very frustrated Tech_Support

Reason: No reason

ernestyn
Posts: 18
Joined: Mon Jul 22, 2019 1:40 pm

Re: DCF 77 77.5KHZ

Post by ernestyn » Mon Jul 22, 2019 4:08 pm

Dear Mike2459 I was very impressed from your sample reception with your smallest antenna and I am interested in your building details. It seems to me you wrote some info down in this articles collection, but now I do not find it, can you help me? Because I need to compare with my circuit before I carry on with my article on antennas.
Last edited by ernestyn on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

VK3MHZ
Posts: 41
Joined: Sun Apr 30, 2017 7:24 am

Re: DCF 77 77.5KHZ

Post by VK3MHZ » Tue Jul 23, 2019 1:45 am

I am very interested in having a crack at this, plus other long-wave broadcasters that are still in transmit mode.
Before I go onto my questions, I will provide some info that may be relevant to the whole gig:
  • I am in a rural country area. Nil power line noise, as all the incoming power lines are routed underground.
  • Space is not an issue, but height is. Unfortunately all the very high gum trees are towards the front of the property, and there is the house and a large row of cypress trees prohibiting me from accessing them.
  • I have a tower of around 7 meters in height, which will eventually be placed down the paddock from my shack as a end-point for long-wires/dipoles.
  • I have another tower, little less than 7.5 meters (can't remember actual length right now, let's say 5 meters for now) which will be placed on top of a shipping container (my shack), so it will be 7.5m to the top of the tower AGL.
  • Receiver - SDRPlay RSP2.
  • Current antenna, 105m long-wire running willy nilly around the place (not in a straight line), ends pointing Westerly.
Think that covers most of the basics.

Questions:
  1. Apart from filters, what are some simple things I can do to improve long-wave reception?
  2. What is a good performing, easy to make antenna for long-wave? Please don't hit me up with formulas and calculations, I am really after a 'simple this is how you make it' design or instruction.
  3. Whilst I have had reasonable success with the long-wire on NDB's within Australia, which I feel isn't a bad effort considering most NDB's run less than 100 watts and are very low to the ground antenna wise. I've never had any luck in receiving broadcast stations. Apart from antennas and filters, is there anything else I can do to improve my success rate?
Last edited by VK3MHZ on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

Post Reply