PortsDown 4 Some questions...

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
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Roberto48
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Joined: Fri Jul 06, 2018 2:04 pm

PortsDown 4 Some questions...

Post by Roberto48 » Mon Mar 02, 2026 2:21 pm

I have build the PortsDown 4 with a Pluto.

It's working great but.... Some questions:

- When I measure the Pluto's output on the various bands, I notice that the 2m band output is more than 3 dB lower than on the other bands. I measured this with both an SA and a PWR meter.

- After I turn off the Tx via the touchscreen, the Pluto continues transmitting for at least 3 seconds.

- When I switch bands/menus, the PortsDown logo briefly appears before switching to the other band/menu.

- I thought the latest firmware also allowed the Pluto to reach 50 MHz. But when I select that in both PortsDown and Langstone, the lowest frequency is 70 MHz. Is 50 MHz not possible, or do I need to configure it somewhere?

I'm curious if anyone else has had the same experience or what a possible solution might be.
Thanks in advance for your answers!

73's
Rob PA0RWE

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G3GJA
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Re: PortsDown 4 Some questions...

Post by G3GJA » Wed Mar 04, 2026 11:48 am

Hi Rob

The output of the Pluto is lower at 2m. To be expected because the Pluto in its unmodified state is advertised as having a range of 325 - 3800MHz.

No, it will not go down to 50MHz with firmware that is compatible with the Portsdown. Other firmware may work at 50MHz but it is not supported on the Portsdown.

The Tx overrun is the buffer in the Pluto taking time to be used up. Expected behaviour. The length of the overrun varies depending on the bitrate.

The logo appearing when switching logos is unusual. More details of your set up would be needed to help with that.

73

Clive G3GJA

Roberto48
Posts: 23
Joined: Fri Jul 06, 2018 2:04 pm

Re: PortsDown 4 Some questions...

Post by Roberto48 » Wed Mar 04, 2026 1:35 pm

Hi Clive,

Thanks for your answers. That's perfectly clear!

My setup is a standard RPI-4 with the latest Portsdown firmware, Pluto, and a 7" touchscreen from AliExpress, as indicated in the Portsdown info.
The Portsdown intermittent screen only occurs when using the Preset buttons. See the attached video. Occasionally, it also happens when using the other buttons. I hope this helps...

Video: https://www.dropbox.com/scl/fi/p5ykg2za ... cjrcb&dl=0

73's
Rob PA0RWE

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Re: PortsDown 4 Some questions...

Post by G8GKQ » Wed Mar 04, 2026 7:55 pm

Hi Rob

The Portsdown Logo is always in the background. If a menu button operation takes a lot of time, the old menu is deleted and you see the background logo until the new menu is constructed and displayed.

Changing a preset makes multiple writes to the Config file on the SD Card (frequency, band, power levels etc) and this can cause small delays.

So nothing to worry about.

73

Dave

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