G8JNJ

I use 75 ohm, foam filled, all copper satellite TV coax, with braid and foil for my active antennas.

Low loss and effective screening, don't worry about the slight impedance mismatch to 50 ohms.

Something like WF100 costs around £30 for 50m.

Don't use stuff with air spacing, or aluminium foil, or copper clad steel.

Regards,

Martin

They are most likely pirates, probably fishermen.

They often like to find "private" frequencies in order to conduct their "private" conversations, and these tend to be on frequencies with number sequences that are easily remembered.

There tend to be lots of them speaking all sorts of Asian languages, and frequently performing lots of chanting.

5 to 12MHz seems to be the most used frequency ranges, but they can pop up almost anywhere.

Regards,

Martin

As I said previously, the majority of Bias Tees have very poor filtering between the DC line and the RF path.

Nearly all the circuits you find on the internet tend to be outlining theoretical designs, that concentrate on providing the least attenuation and impedance "bumps" in the direct RF path, but don't worry about what happens with RF entering via the DC path.

The better designs for our reception purposes, incorporate additional filtering components in the DC path, in order to reduce this problem. But very large values of L and C are required in order to be effective at the low frequencies, especially at less than 100kHz.

Regards,

Martin

Check the antenna Bias Tee first.

Many don't have enough filtering built into them.

Regards,

Martin

I have noticed a problem, where folks stay connected or a long period, but they are only viewing the waterfall or spectrum display, and maybe doing something else.

So the frequency and mode they have selected, are sometimes misleading with regard to the purpose the KiWi is being used for.

This is usually indicated by being fully zoomed out e.g. z0

Regards,

Martin

Before swapping supplies, make sure that it is the Apple power brick that is causing the problem. It may well be something else.

The signal will most likely change its characteristics if the power supply load is altered in some way.

Try a different make of supply and see if the interference on that frequency changes or goes away completely.

Regards,

Martin

There are so many amateur digital modes these days, it is often very difficult to say what is being used.

It is around the frequencies typically being used for SSTV, and it could be Digital SSTV, but that is just a guess on my part.

The Signal ID Wiki is a good place to start when trying to ID unknown signals.

https://www.sigidwiki.com/wiki/Signal_Identification_Guide

Regards,

Martin

Hi Andy,

I understand the points you are making, but having previously discussed this with Philippe, I think there are some valid concerns, that may discourage other people, in other countries, from operating a KiWi.

If a simple fix, which John has already implemented, can help remove some of these barriers, then surely it is a good thing ?

Some countries are extremely sensitive about some aspects of the radio hobby, and to be honest, if I was living in one, I wouldn't be running a KiWi. It's easy to forget this when living somewhere that is more "relaxed" about such things.

Callsign piracy has always been an issue, and using an alpha-numeric string (or emojis) to identify an individual doesn't mean that they are who they say they are. However, I can understand the problem for the KiWi admin, if someone else decides to use your callsign, and you, the legitimate owner, find out, and then blame the admin for something that he has no control over. This may sound unlikely, but I have experienced similar problems when we had the "Chat" facility enabled on one of our websdr's, which caused so many issues we, (like most other websdr admins) removed it. Any public site, that has the ability for folks to anonymously post comments, no matter how brief in content, will unfortunately be abused.

Andy - "they" already know, who you are and where you are :-)

Regards,

Martin - G8JNJ ( or am I )

Hi Glenn,

I have used WSPR Daemon with good results, but unless you have set aside some KiWi channels to allow it to run, it's not really applicable to the average KiWi installation.

Although not calibrated against a known noise reference, the graphs I have obtained using the standard KiWi SNR stats are almost as detailed as the ones I obtained using KiWi Daemon, in therms of indicating propagation changes. But unlike WSPR Daemon, it's a background process and doesn't require additional resources such as a RasPi (scarce at the moment), or consume precicous receive channels in order to work.

In addition I feel that the use of WSPR is beginning to wane somewhat, and FT8 is now taking over the world of Amateur radio. In fact if FT8 had a mechanism for reporting transmitted power and a full 6 digit locator, as does WSPR, I think WSPR would be in further decline for use as a propagation indicator.

With this in mind, it would be nice if the KiWi could support more of the JT/FT modes as an extension, in addition to WSPR, as I believe the libraries are available, but I guess it's not particularly high on the adgenda for John these days.

Regards,

Martin

Sometimes, when used inside a Switched Mode Power supply, the additional choke inductor in the ground (L3 in the circuit) can sometimes be more problematic than useful.

I tend to wire the DC 0v / -ve directly to the mains earth, but depending upon the local configuration, this can also make things worse.

Unfortunately, it's one of those cases where, although it may be good practice to do certain things, you generally have to experiment, in order to find the best solution for your own setup.

Regards,

Martin