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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

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

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