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Recording QSO’s From My Shack

Since my new Wouxun has audio output jacks, I figured it would be useful to have the ability to record what my rig hears, if anything interesting comes on the air.

Under Linux, I use an application called, (creatively enough), Audio Recorder.

Recorder Screenshot
Recorder Screenshot

Using a simple connection to the mic input on a USB soundcard, I can capture everything the radio hears. Unfortunately this doesn’t work for outgoing audio, so it’s not much good at capture of my personal QSOs. For this I will have to set up another radio to act as the main receiver.

At some point in the future I will implement this with a Raspberry Pi as the audio capture server.

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Wouxun KG-UV950P RF Power Measurements

Following on from the earlier power tests on my Baofeng HTs, here’s the readings from the Wouxun KG-UV950P. Power is a little lower than specified, but this is probably due to the supply voltage being a bit less than 13.8v. These readings were taken at a supply voltage of 12.88v.

The same frequencies were used, 145.500 & 433.500 for the VHF/UHF tests. For the 6/10m tests 27MHz & 50MHz were used.
The power meter was connected with 1 metre of RG58 dual-screened cable with N-type connectors.


 High


6m: 24W

10m: 23W

VHF: 38W

UHF: 24.9W


Medium-High


6m: 10.9W

10m: 9.3W

VHF: 19W

UHF: 14.2W


Medium-Low


6m: 6.8W

10m: 3.5W

VHF: 9.6W

UHF: 9.4W


Low


6m: 3.5W

10m: 1.9W

VHF: 4.8W

UHF: 4.7W

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Wouxun KG-UV950P Band Unlocking

I have recently come across the software the Wouxun factory uses to set the band limits on the KG-UV950P.

While the software is in Chinese, it’s functional, and allows setting of all band limits on the radio.

Here’s an English version of the interface:

Limit Setup Menu
Limit Setup Menu

Note when using this software:

This possibly has the potential to damage the radio, if you transmit on a frequency it’s not designed for. Not to mention the legal issues with transmitting on frequencies that aren’t permitted! Use at your own risk!

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Wouxun KG-UV950P Teardown & Analysis

Following on from my review, here are some internal views & detail on the components used in this radio. Below is an overview of the main PCB with the top plate removed from the radio.

Cover Removed
Cover Removed
RF Final Amplifier Stage
RF Final Amplifier Stage

Most visible are these MOSFETs, which are Mitsubishi RD70HVF1 VHF/UHF power devices.  Rated for a maximum of 75W output power at 12.5v (absolute maximum of 150W, these are used well within their power ratings. They are joined to the PCB with heavy soldering, with bypass caps tacked right on to the leads.

RF Pre Drivers
RF Pre Drivers

Here is the RF pre-driver stage, with intermediate transistors hidden under the small brass heatspreader.

Power Section
Power Section

In the top left corner of the radio, near the power input leads, is the power supply & audio amplifier section. Clearly visible are the pair of LA4425A 5W audio power amplifier ICs, these drive the speakers on the top of the radio. Either side of these parts are a 7809 & a 7805 – both linear regulators providing +9v & +5v logic supplies respectively. The large TO220 package device is a KIA378R08PI 3A LDO regulator with ON/OFF control, this one outputs +8v. Just visible in the top right corner are the sockets for the speaker connections.

DTMF Circuits
DTMF Circuits

Here are the two ICs for dealing with DTMF tones, they are HM9170 receivers.

Glue Logic
Glue Logic

In the corner next to the interface jack, there are some CD4066B Quad Bilateral switches. These make sense since the interface jack has more than a single purpose, these will switch signals depending on what is connected.

RF Section
RF Section

Here are visible the RF cans for the oscillators, the crystals visible next to the can at the top. The shields are soldered on, so no opening these unfortunately.
Also visible in this image is a CMX138A Audio Scrambler & Sub-Audio Signalling processor. This IC deals with the Voice Inversion Scrambling feature of the radio, & processes the incoming audio before being sent to the modulator.

Output Filter Network
Output Filter Network

Shown here is the RF output filter network, this radio uses relays for switching instead of PIN diodes, I imagine for cost reasons. The relay closest to the RF output socket has had a slight accident 🙂 This is slated to be replaced soon.

RF Output Jack
RF Output Jack

Finally, the RF output jack.

Audio Speakers
Audio Speakers

Here the speakers are shown, attached to the bottom of the top plate. They are both rated 8Ω 1W.