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All the broadband routers I have had provided, have had noisy Switched Mode "Wall Wart" type power supplies as standard.

They produced far more interference than the routers, which generally tended to be of good construction and had been EMC tested as part of the design process.

The power supplies always seemed to be an afterthought, and may have been sourced differently from the actual router, depending on local electrical regulations and requirements.

It is likely that the power supplies have been chosen on the basis of cost, and we all know what happens then.

Because of their small size, it is usually not possible to add extra filtering, and such internal modifications can also result in safety and insurance issues.

I tend to look in Charity (Thift) stores or at Car Boot sales for older, cheap electronics, with separate linear power supplies. As it's difficult and expensive to buy new linear power supplies, especially since the audiophiles are willing to pay silly prices for them. The rest of the electronics are useful for parts too.

On an incidental, but related subject

A friend of mine, who allows me to host a KiWi at the historic Goonhilly satellite earth station in Cornwall UK, was good enough to resite the KiWi to a new location on the site, in an attempt to resolve some long standing interference problems. However, he couldn't get it to connect properly to the network. He could see it acquired a DHCP address, but he couldn't ping it. He then transferred the KiWi back to the original location, and it still didn't work properly.

Thinking that somehow the build had become corrupted, we arranged for him to return the KiWi to me, so that I could fix it, upgrade the OS and take the opportunity to check things like the fan (which as expected was stuck solid).

The actual fault was the Switched Mode Power supply, which seemed to be working correctly, as the output voltage was correct when checked with a multimeter, it would also still happily deliver 5A output.

However, I noticed that the output voltage dipped just a bit more than I would have expected when on load, but only by about 0.2v.

I took the power supply apart and discovered that the main high voltage DC storage capacitor (150uF at 450v) had dried out over time, and was completely open circuit. This is why the DC regulation was so poor, and also why the KiWi was having difficulties.

Replacing the capacitor fixed the problem, and the KiWi was back to working as normal.

Most of my past KiWi problems have been power supply related in one way or another, so my rule of thumb now is:-

If your KiWi is misbehaving in any way, check the power supply first, and pay close attention whilst you do it.

Regards,

Martin

When using an MLA-30, I don't think you can have too much gain :-)

Auto waterfall settings can have you chasing your tail. So I tend to set the KiWi waterfall & Spectrum display to manual, zoom fully out to see the whole spectrum, then set the maximum waterfall level to -20dB and the minimum to -110dB. This gives a good baseline for comparison with other KiWi's when the same settings are used on them too.

Don't worry about the noise increasing, you should see some, especially in an urban environment.

Just aim for a 6dB increase in the noise floor on the upper HF bands 20-30MHz, when the MLA-30 is powered up.

As I said before, turn the bias tee control to maximum gain, and then just use the amplifier gain control to achieve the best overall performance.

Regards,

Martin

"Seems the interface is a bit slicker."

Not really, it's just different, and has as many "quirks and foibles" as the KiWi (sorry John).

OpenWebRX + is more orientated to the VHF / UHF bands, and is good at the modes that can be found there, and I operate both.

However, the developers are not as responsive as John, and the admin interfaces and configuration processes require a good degree of skill to set them up and make them function correctly.

By contrast, the KiWi works pretty much straight out of the box and is generally stable, OWR+ is more of a work in progress.

This may suit folks proficient in Linux, who enjoy spending many hours resolving problems, but some of us just want something that works, with minimal hassle.

Regards,

Martin

For transmit purposes, it's all about antenna efficiency, and radiating as much of the applied RF power in the direction you want it to go.

For reception purposes, it's all about the Signal to Noise Ratio, and a good transmit antenna may not always be a good receive antenna.

The natural noise floor on the LF bands is relatively high, especially in urban areas, and even quite small antennas can still be performance limited by the surrounding noise floor.

Rather than concentrating on large antennas, you may get better results with a smaller antenna in an electrically quieter location. Some experimentation is required, to get the best results.

Balanced antennas are generally better than unbalanced ones, and end fed wires have a reputation as being noise magnets.

If you do wish to install one, this diagram may provide some suggestions about minimising unwanted noise.

Regards,

Martin

I should have clarified the way it works a bit better.

Pushing the mouse wheel down whilst rotating it enables the opposite mode to the default that has been chosen. in OpenWebRX.

Having the possibility to tune using the mouse opens up other possibilities such as making your own VFO knob, using the optical encoder recovered from a scrap mouse, or buying one of the more expensive ready-made commercial items.

If it could be implemented in a way similar to that of OpenWebRX , then it would still retain the mouse wheel zoom option for those who prefer it, but offer an alternative for folks who would like to use mouse wheel tuning.

Try it and see for yourself.

http://wessex.hopto.org:8060

If you open up the settings pane in the control panel, you should see the "Hold mouse wheel down to tune" tick box. Also set the tuning step size in the controls section, 500Hz or 1kHz is useful for SSB, as most folks use 'rounded up' frequencies.

I'm not specifically requesting this feature, as I don't wish to add to John's already massive workload of much more important issues, but I can understand the appeal of it.

Regards,

Martin

Hi John,

Not a big deal, but it may be related to the mouse behaviour.

I notice that sometimes when I click on the waterfall, the KiWi doesn't tune to that frequency, but it remains on an existing frequency. A second click is then required before it tunes correctly.

I have only noticed this over the past month or so, but it may have been like this for a while.

Regards,

Martin

The gain control on the bias tee is a passive one, so it's probably best to set that for minimum attenuation and maximum signal levels anyway.

Then adjust the gain control on the loop amplifier board.

There is no point adding more gain than necessary in the loop amplifier, only to counteract it by applying attenuation later in the signal chain.

Ideally, you should aim for approximately 6dB increase in the KiWi noise floor at frequencies around 20 to 30MHz, when the antenna is powered.

Any more than this, and you will not improve the Signal To Noise Ratio, but you will be eating away at the receiver's dynamic range, and making it more prone to overload on strong signals.

A 6dB increase in noise floor, when the antenna is connected, is the "sweet spot" to aim for.

Regards,

Martin

This is a typical data sheet for the type of ceramic patch used in the small GPS puck.

https://datasheets.kyocera-avx.com/ethertronics/AVX-E_1001039.pdf

Note the 70x70mm PCB ground plane used in the measurement test setup.

The 30x30 PCB inside the puck is really just a bit too small, and the polar diagram and off-axis noise rejection is improved by having a larger ground plane below it.

Many of the external GPS antennas are basically just the guts of a puck, mounted on a larger ground plane, and inclosed in a waterproof housing.

Regards,

Martin

I watched one of Techmind's video's relating to the End feed antenna.

https://youtu.be/VYt3-jkBfaQ?feature=shared

Some things of note.

He is on the edge of rural farmland, so the noise floor will be lower than if he was in the middle of at typical UK housing estate, it is also likely that his utility services will be buried rather than being carried by overhead wires, which will further improve the noise floor.

He has installed the antenna in the best way possible, with the feed point located way from the property, and he has also installed a choking balun and separate RF ground, although this could be further improved. Ideally, he should also have incorporated some form of galvanic isolation, in order to reduce the risk of ground loops, or possible issues with UK wiring regulations and mains safety.

Regards,

Martin

I wouldn't trust a Chinese made torque wrench.

It's unlikely that the KiWi will be repeatedly connected and disconnected as much as some other equipment.

Slightly past hand tight is fine, and don't use a big adjustable wrench.

Regards,

Martin