Beitrags-Archiv für die Kategory 'Uncategorized'

Kenwood TH-D75 frequency expansion (MARS/CAP mod)

Dienstag, 6. Februar 2024 18:24

The TH-D75 has a resistor matrix consisting of 4 resistors (R1, R2, R3, R4) which are of SMD 0603 1k type. 2 of them (R1, R2) are accessible in an easy way and labeled on the top PCB in the lower left corner.

In the usual case it should be enough removing R1 (be careful) in order to open the TX range on a TH-D75E.

The „E2“ version (with maximal TX frequency range) looks in detail the following:

R1 removed
R2 installed
R3 installed
R4 removed

R3 and R4 (on the rear side of the PCB) should only be checked in seldom cases when just removing R1 doesn’t give the expected result.

In the E2 version all functions (e.g. Automatic Repeater Shift ARS) will remain – just the TX range is „open“.

As read in several articles in various forums for the TH-D75A removing R2 will expand the TX range. The default configuration of R3 and R4 for the American version is currently unknown.

An unimportant note: while trying different combinations R1 installed, R2 removed, R3 installed, R4 removed will result in a kind of Japanese version.

A photo of the rear side of the PCB in order to determine R3 and R4:

Thema: Uncategorized | Kommentare deaktiviert für Kenwood TH-D75 frequency expansion (MARS/CAP mod) | Autor:

IC-905 frequency expansion

Samstag, 5. August 2023 22:53

under investigation…

Thema: Uncategorized | Kommentare deaktiviert für IC-905 frequency expansion | Autor:

some thoughts about DATV on QO-100

Mittwoch, 15. Februar 2023 23:28

After having setup my narrowband equipment a few years ago I had the goal of operating wideband (DATV) too. With my existing Kuhne downconverter and the BaMaTech feed with 2 outputs for 10GHz it was easy to connect a SMA coaxial relay directly near the feed to switch polarization by the switching output of the downconverter. Connecting an ELAD E-Tiouner, powered with about 18-20V input voltage (input voltage = output voltage on F-connector) makes the downconverter switching to the correct LO frequency (9240MHz) and triggering the switching output to ground that makes the coaxial relay switch to horizontal polarization. Using the MiniTiouner software provides the possibility to decode even low symbol rates (from 66kS) and quickly switching of frequency and all other necessary parameters according to what you see in the wideband spectrum.

The TX topic is slightly more complex. There are a few approaches to generate a DVB-S2 signal in a „cheap“ way. First of all I want to clarify that I do respect all the work done by these developers that were involved in all of those projects (e.g. F5OEO, IS0GRB, F5UII – only to mention a few).
During some weeks of trying to find a reasonable, stable and convenient solution to modulate the DVB-S2 signal I was gleaning a lot how others solved this. Software solutions like DATV-Easy, DATV-Express, Portsdown, etc. together with the ADALM Pluto or LimeSDR appear everywhere. I tried every of them with more or less satisfaction. F5OEO’s solution (PlutoDVB) of using the Pluto with a special firmware to receive a RTMP or UDP stream and encode it into DVB-S2 is not bad from the start. The versioning disaster and the different patches don’t make it very easy to find an all-working and reliable version. As I saw, many operators only concentrate on generating glamorous content but not fixing basic issues. How and with the help of which software or encoder the video stream is generated is only secondary in my opinion.

After many weeks I personally came to the conclusion that I want to have a better (maybe the luxury) version for me, and started to investigate which possibilities of commercial DVB-S2 modulators exist.
The parameters: direct output frequency 240xMHz without the need of converting anything, the ability to use low symbol rates, an output power that is able to drive the next stage PA (around +15dBm) and the use of several input streams (UDP, RTSP, etc.) together with a possibility to stream a fixed TS file.
The object of desire: Rohde & Schwarz SMCV100B with the SMCVB-K167 / SMCVB-K519 options.

Some of those reading this might think that it’s a crazy and expensive solution – indeed it is! – but it is not more crazy than operating an IC-7851 or a PT-8000 for shortwave… 😉

Thema: Uncategorized | Kommentare deaktiviert für some thoughts about DATV on QO-100 | Autor:

IC-9700 crossband repeater

Freitag, 2. Dezember 2022 0:12

Thema: Uncategorized | Kommentare deaktiviert für IC-9700 crossband repeater | Autor:

CB handheld radio – President Randy III – TX audio improvement

Donnerstag, 23. Dezember 2021 19:45

to gain a slightly better (louder) TX audio enter the radio’s service menu by holding ANL/NB and SCAN while powering on and toggle to the menu entry FM MOD. Now press PTT and set the value to 511. You may find out that the maximum numeric value is 512, but 512 is the same setting like 0 – so 511 is really the maximum deviation you can adjust the radio to.

Thema: Uncategorized | Kommentare deaktiviert für CB handheld radio – President Randy III – TX audio improvement | Autor:

ID-52 TX modification (MARS mod)

Samstag, 18. Dezember 2021 19:09

to expand the VHF/UHF TX frequency follow the instructions according to the picture by removing 2 diodes

Thema: Uncategorized | Kommentare deaktiviert für ID-52 TX modification (MARS mod) | Autor: