Re: rewinding a PL-380 antenna


sdwillingham
 

--- In ultralightdx@..., Rick Robinson <w4dst@...> wrote:
Thank you for clearing up my misunderstanding regarding the RSSI
readings being taken from the input not the output of the LNA. That
makes the radio almost a low cost selective voltmeter.
Yes, the RSSI readings are pretty accurate for most uses (especially
for relative readings). They could easily be calibrated with an
external attenuator for even more absolute accuracy. At very strong
RF levels, the readings may deviate for a couple of technical reasons.

I've noticed
that my PL-380 "updates" the RSSI/SNR info on the screen more frequently
than the G8. Is this my imagination or a programmable parameter in
firmware?
The screen in each radio is controlled by Tecsun's main application
processor. The processor sends query commands to the Si4734 to obtain
the RSSI numbers. The update rate is determined by Tecsun, probably to
reserve battery power and keep RF interference to a minimum. The Si4734
internally updates the RSSI and SNR parameters at much higher rates.

According to
the Si473X data sheet there are 7 different bandwidths. What are the 2
not implemented in the PL380?
The PL-380 uses the Si4734-B20 variant of the chip, which has version
2.0 of the Silabs' firmware. The C40 version of the chip adds 1.8 and
2.5 kHz filters. Although 1.8 kHz is very close to 2.0 kHz, I think
there are differences in the detailed filter response for better
intelligibility and adjacent channel rejection.

I'll also offer a tip of the hat to the FM section of the Si4734 which
is also amazing. Is anyone using or planning to use the '4735 with RDS
decoding that you are aware of? I'd love to see this in a future ULR
although the increased size of the LCD to incorporate RDS data and the
cabinet to support it, would most likely take it out of ULR class.
The FM section is the "bread-n-butter" of our revenue stream and is
highly refined. The RDS performance is the best in the industry in both
performance and ease of use. Many devices make use of this chip (minus
the AM functions), just in a different form factor than you are used to
looking for: Zillions of cell phones, "Personal Navigation Devices"
(GPS) which use the RDS decoding for traffic info, pre-HD versions of
the Zune mp3 player, Apple's FM radio accessory for iPods, the 5th-gen
iPod Nano, and many other mp3 players.

As for future "conventional" ULRs with RDS features, I don't have any
information about that.

-Scott-

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