Best RX's for long distance anorak signals....

[EFR]

If you want quiet outdoor antenna for FM band, go to an folded dipole or full wave loop, with loop you can null noises from neighbours.

Build about 102cm long horisontal and 51cm tall vertical parts, feed from center of 51cm part.
No baluns or anything needed.

Measurements are from my head, might check them with calculator, but they are close.


Like this:

Code: Select all

120CM
____________________
|                   | Feed here from middle.
|                   | 51cm tall part.
____________________

Use some PVC etc pipe to hold it up, bend it from 4mm aluminium tube or wire.

For mounting it to the PVC pipe, drill hole about 25.5cm from top, feed coax truh it and solder/crimp it to the wire/tube using you favorite method.

Pull that loop wire/tube near PVC tube and use some zipties/tape to secure it to the side of pipe.

If you want one vertical, just turn it so that 102cm part is up, feed from middle of 51cm part.

[Albert H]

I have another amplified, portable aerial that I sometimes use, is based on an old Elektor design called the "Omega Aerial". It's performance is really good, but it's not as convenient as it's a loop design. It's sometimes useful to null out directional interference, however, as it's very directional.

[EFR]

Whip-Aerial.png

Thats a quite classic one!

It is. The only (minor) problem with it is that the FET can be killed by static. It also runs warm because of the low value emitter resistor for the 2219. We had some snow about 2 weeks ago, and the aerial was covered with snow and ice in the morning, but the little tubular can that contains the amplifier was clear of snow!

Old modifield was like Vishay +100Mohm thickfilm resistor from fet gate to ground, and that 1Mohm resistor was something "little bit lower value", dont remember what.

[radionortheast]

I can confirm that both the PL-310ET and DX-286 have internal ferrite bar aerials which work fine. Haven't tried LW on the DX-286 yet, it's disabled by default but easy to switch back on. I don't know about the TEF radios like the one in the picture on FMEnjoyer's post above, but the "desktop" TEF I bought which started off my interest in this chip has an internal antenna which is switchable on the back. Performance is nothing to write home about in fact you won't even be buying a stamp - I think the unit itself generates too much internal noise to bother.

I did wonder what the tef was like on mw, its what I use here for fm, sounds like its not so good on mw, it dosen’t have a ferrite bar antenna so i’ve not been able to use it here. The other thing is weather a radio can tune to the dutch pirates above 1602khz, weather it would be easy if something is not set up by default. I use the fm aerial for listening through sw with the tef, it dose pick up well, there is quite alot of noise.
I think car radios do often suffer from internally generated noise too, would make listening to a weak or low power signal impossible now, along with the in car transmitters, I suppose another subject. I did use a car radio powered by a 12v supply before they started putting the chip inside standalone radios they do work very well, the jvc kd-x262 is a good one, a stylish number

[FMEnjoyer]

If you want quiet outdoor antenna for FM band, go to an folded dipole or full wave loop, with loop you can null noises from neighbours.

Build about 102cm long horisontal and 51cm tall vertical parts, feed from center of 51cm part.
No baluns or anything needed.

Measurements are from my head, might check them with calculator, but they are close.


Like this:

Code: Select all

120CM
____________________
|                   | Feed here from middle.


|                   | 51cm tall part.
____________________

Use some PVC etc pipe to hold it up, bend it from 4mm aluminium tube or wire.

For mounting it to the PVC pipe, drill hole about 25.5cm from top, feed coax truh it and solder/crimp it to the wire/tube using you favorite method.

Pull that loop wire/tube near PVC tube and use some zipties/tape to secure it to the side of pipe.

If you want one vertical, just turn it so that 102cm part is up, feed from middle of 51cm part.

Thanks for the suggestion. I recall the noise will dropping off once outside must be some wacky Chinese PSU letting off the nasties over the band.

[shuffy]

Does anyone know if the TECSUN external antenna sockets really work ?
Is this essentially a mono mini jack + and - and would 50 Ohm coax run be ok ?

Yes and yes it does work, on my PL-310ET at least. Make sure the earth side is connected to your feeder, it makes a big difference.

I added wire to the PL-310 and DX-286 antennas to make both 80cm long and did my basic comparison again. Both radios performed a little better but I still think the PL-310 pulled the stations in a tiny bit better - not much in it to be honest. There's still a 2-3dBu difference in the meter readings. Same story on shortwave with the meter but I'd say the DX-286 won here as it dealt with the fading better than the TECSUN.

I did wonder what the tef was like on mw, its what I use here for fm, sounds like its not so good on mw, it dosen’t have a ferrite bar antenna so i’ve not been able to use it here. The other thing is weather a radio can tune to the dutch pirates above 1602khz, weather it would be easy if something is not set up by default. I use the fm aerial for listening through sw with the tef, it dose pick up well, there is quite alot of noise.

I disagree, the TEF chip is good on MW/SW. Follow the link to Barney's TEF that I posted earlier on this thread and have a play with it. From my experience with the desktop TEF, I assume that the ESP32 SoC they're using is noisy enough to make an internal ferrite bar pretty pointless for AM. You probably always want an external antenna as far away as possible from the radio. Also different TEF modules / radio designs connect the antenna to the chip differently so that's something to be careful of if you can.

MW on my DX-286 (probably configurable) goes up to 1710kHz so with a decent antenna you should get those pirates up the top end of the band. Actually I think you can get the full range of the TEF chip on HF (up to 27Mhz?) but from 1711kHz the frequency will be mapped to one of the shortwave meter bands. Hope that helps.

[radionortheast]

Thanks Shuffy, suppose you could rig up a traditional transformer to power something, get less noise, an effort to go to, smps are more efficient, I did think about it once or twice, I decided I would use the pocket sangean orientate it to get the dutch pirates.

[shuffy]

Thanks Shuffy, suppose you could rig up a traditional transformer to power something, get less noise, an effort to go to, smps are more efficient, I did think about it once or twice, I decided I would use the pocket sangean orientate it to get the dutch pirates.

It's not just the PSU - the chip needs a controller of some sort to send commands to it. Most of the Chinese TEF radios use an ESP32 (SoC) and will pick up digital crud from this on the HF bands especially. Shielding and careful overall design will help but if the controller is in the same box as the radio chip and you're using an internal antenna for these bands, you're not starting from a good place.

Different types of controllers perform differently in this respect of course. The headless TEFs I've been making recently are ultra simple (and cheap) using an ATMEGA328 (arduino nano) which don't appear to be that noisy - certainly better than the ESP32 and possibly better than a PIC.

[radionortheast]

I realised after posting with that radio it might be more internally generated stuff, I used hear ury with the car radio mentioned earlier on, it was suprizing because I was using an smps, the aerial at the time was a pushed through the roof on a long pole, this was on mw btw. Since I moved the aerials been in the loft, couldn’t be used for mw anymore, it only sits afew meters above me here, there was no hole to put it through I suppose it would also stand out abit more here. So the car radio with the tef I mentioned would likely work very well on mw I don't know if you could tune it above 1602khz though

[Albert H]

Different types of controllers perform differently in this respect of course. The headless TEFs I've been making recently are ultra simple (and cheap) using an ATMEGA328 (arduino nano) which don't appear to be that noisy - certainly better than the ESP32 and possibly better than a PIC.

One design I saw recently put the Arduino into a "sleep" state once the tuning info had been loaded. Turning the rotary programmer "woke up" the Arduino. The delay before the Arduino shut off was a couple of seconds, and the receiver was relatively "deaf" until the "sleep". Unfortunately, this meant that tuning across the band would miss all but the strongest signals.....

As ever, electronic design is compromise!

[shuffy]

One design I saw recently put the Arduino into a "sleep" state once the tuning info had been loaded. Turning the rotary programmer "woke up" the Arduino. The delay before the Arduino shut off was a couple of seconds, and the receiver was relatively "deaf" until the "sleep". Unfortunately, this meant that tuning across the band would miss all but the strongest signals.....

I'm always conscious of going off topic on these but here goes. Maybe we need a "TEF" thread.

With these types of receiver I just don't think you can do without the microcontroller, full stop.

For the case with your RX with the rotary controller, scanning or anything involving evaluation of the signal metadata just isn't going to work without the microcontroller. You could put it to sleep after tuning but you're going to get no signal data and potentially no audio either depending on your implementation.

For me though, the most compelling use case for the TEF RX is running headless and being online 24/7 plus scanning, logging, recording etc. If you want to use existing applications like the fmdx webserver stuff and clients like xdr-gtk, then at the very least your RX needs to follow the "xdr protocol" to allow it to interact. This means you need a controller connected to the TEF chip which is continuously listening for commands from the client and sending back signal and system data, and audio too if you're using the I2S rather than its built-in DACs.

Even the bespoke monitor application I wrote (originally I was using a Pi model 1 which couldn't do a node.js build) which was pretty low level, was using XDR protocol to talk to the radio. This was implemented in the Arduino.

In the room where I have my prototype headless TEF running right now, there's 15dBu of crud mostly coming from the wifi extender and it makes its way close to the RX up the cables coming from the Raspberry Pi 3B I'm now using as a server. The radio has an external antenna outside so it's not too bad on VHF but if I decide to try and make it usable on HF, then there's work to do.

Surprisingly there's not much noise coming from the Pi itself - most of the HF noise seems to be coming from the external ADC I'm using which is a lash-up at the moment and can be tidied up. The crap from the Arduino is minimal, about 2dBu extra, so I'm going to keep this and concentrate on shielding and filtering and see how much this can improve matters.

[Albert H]

Sounds good, Shuffy. Keep us all up to date with progress, and if you get really good results, some circuits and software would be welcome!

[shuffy]

I can't take much credit for the circuit or firmware. I've changed them a bit but they are from the original "headless" Arduino design, prior to the current ESP32 TEF radios but still available on github. I just got the (cheapest) current TEF module from Aliexpress and hacked everything else to fit, ending up with my own version. The client comms protocol has stayed the same all along, so my cheapo headless TEF works with clients including xdr-gtk and fmdx webserver just the same as a modern ESP32-based job, and the performance is comparable.

The one thing that I don't really like is having to use an ADC to capture audio for streaming as the TEF module I chose doesn't expose the chip's I2S interface. I'm using an external PCM1808 board on the Pi with darkice/icecast, but it still sounds very good. Making the ADC work on the Pi was actually the hardest part of the whole project so far.

If there's any appetite for "necks" building something like this then I'll post the links to the designs I started from, and maybe some pics of what I did. For now though, I'll shut up as it wasn't really the point of this thread...