Search found 857 matches

by Daniel Wee
Wed 24 Mar 24 2021 7:29 pm
Forum: General Discussions
Topic: SARTS Repeaters
Replies: 19
Views: 3664

Re: SARTS Repeaters

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by Daniel Wee
Tue 23 Mar 23 2021 4:26 pm
Forum: General Discussions
Topic: SARTS Repeaters
Replies: 19
Views: 3664

Re: SARTS Repeaters

VHF Duplexers Telewave TPRD-1444C Min. separation: 600kHz Insertion loss: 1.5dB Rejection: 70dB Weight: 8.7kg USD2267.33 https://www.tessco.com/product/135-151-mhz-compact-pass-reject-duplexer-517711 https://www.talleycom.com/viewProduct?rlProdNum=TELTPRD-1544C Telewave TPRD-1554 Min. separation: 6...
by Daniel Wee
Fri 19 Mar 19 2021 7:18 pm
Forum: General Discussions
Topic: SARTS Repeaters
Replies: 19
Views: 3664

Re: SARTS Repeaters

Tuning procedure 1. With all cabling harness in place - connect VNA port 1 to TX port and port 2 to the Antenna port. 2. Disconnect the RX-side and the connection to cavity 1 (TX) 3. This leaves only cavity 2 (TX) connected On cavity 2 (TX) 1. Adjust the flange rotation to get exactly 600kHz separa...
by Daniel Wee
Fri 19 Mar 19 2021 6:07 pm
Forum: General Discussions
Topic: SARTS Repeaters
Replies: 19
Views: 3664

Re: SARTS Repeaters

Retuning the Cavity (again)

1. It looks like all cavities affect the final tuning. The TX cavity can be perfectly tuned but the moment the RX cavities are connected - everything goes off.
S21 from TX port to antenna without RX-side
S21 from TX port to antenna without RX-side
S21 TX-Ant without RX.png (9.85 KiB) Viewed 311 times
S21 from TX port to antenna with RX-side connected
S21 from TX port to antenna with RX-side connected
S21 TX-Ant with RX.png (10.71 KiB) Viewed 311 times
by Daniel Wee
Mon 15 Mar 15 2021 7:29 pm
Forum: General Discussions
Topic: SARTS Repeaters
Replies: 19
Views: 3664

Re: SARTS Repeaters

Cavity Inspection and Tuning 0. Duplexer model is Telewave TPRD-1554 Screenshot 2021-03-15 215846.jpg spec-18.jpg desc-16.jpg http://www.telewave.com/product/tprd-1554-pass-reject-base-station-duplexer-144-174-mhz/ [yt]https://www.youtube.com/watch?v=tD1upx4-DDI[/yt] 1. Cavity #2 (TX) coupling loop...
by Daniel Wee
Sun 14 Feb 14 2021 8:33 pm
Forum: Radios
Topic: ICOM IC-7300 and IC-9700
Replies: 2
Views: 831

Re: ICOM IC-7300 and IC-9700

The IC-7300 uses an MP7741 audio power amplifier IC in quite an elaborately filtered configuration.
by Daniel Wee
Sun 14 Feb 14 2021 8:23 pm
Forum: Radios
Topic: ICOM IC-7300 and IC-9700
Replies: 2
Views: 831

Re: ICOM IC-7300 and IC-9700

Documents for the IC-9700.
by Daniel Wee
Sun 14 Feb 14 2021 8:22 pm
Forum: Radios
Topic: ICOM IC-7300 and IC-9700
Replies: 2
Views: 831

ICOM IC-7300 and IC-9700

Approved for use in Singapore. The following are the documentation and service manual.
by Daniel Wee
Sun 14 Feb 14 2021 11:55 am
Forum: Radios
Topic: Yaesu radios' audio output stages
Replies: 2
Views: 812

Re: Yaesu radios' audio output stages

Interestingly, ICOM also uses the LA4425A in the output stages, for example in the IC-718 (pg.16 of attached file). This has been confirmed to exhibit that hiss at zero volume as well.

The FT-DX101MPD, on the other hand, uses the TDA2003 power amplifier chip.
by Daniel Wee
Sun 14 Feb 14 2021 10:47 am
Forum: Radios
Topic: Yaesu radios' audio output stages
Replies: 2
Views: 812

Noise in output

The noise in the output of the amplifier does not change with volume, so it must be inherent to one of these three parts - the M62364FP, NJM2737 or the LA4425A. The NJM2737 is specifically a low noise part so I'm not suspecting it as a noise source at the moment. The M62364 has only 8-bits so it is ...