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Reviews For: DF4ZS RF speech processors

Category: Audio Accessories for Transmitter & Receiver

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Review Summary For : DF4ZS RF speech processors
Reviews: 15MSRP: 65-130
Increase average SSB power of radios without RF speech processing by up to 9 db without excessive distortions; smallest model fits into a microphone; make IC-706 or FT-100 sound like with a 400 W amplifier
Product is in production
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# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
G7DDN Rating: 2018-03-26
Like a Datong for your FT-817 Time Owned: 0 to 3 months.
I purchased one of these sometime before Christmas and for various reasons, didn’t get around to fitting it until this week.

One reason was that I was unsure how difficult it would be to install, but following the instructions carefully, it was, in the end, no big deal.

But what a difference! Just playing around listening through headphones to my signal when setting up, I could tell this was going to make a huge difference.

My friends on 160m tell me it sounds just like the old Datong RF speech processors of old, which many used, and still do, if you can find them, for contesting.

With QRP SSB you really notice the difference, both in the tx audio and in the reports you get back from other hams.

So good, in fact, that people won’t believe it’s an 817! Nice!
GW6KLQ Rating: 2017-10-26
Gives real punch to FT817 QRP Time Owned: 6 to 12 months.
Added one of these to the FT817. Working /p in Portugal first call on 10W was answered by US station.
Audio quality is good for heavily processed audio. Good intelligibility. Was easy to fit and makes a huge difference.
DC3AFA Rating: 2014-05-03
Great improvement for FT-817 Time Owned: more than 12 months.
Using this speech processor for nearly 4 years now and will recommend it again an again. It´s one of the best things you can do to your FT-817!
14FRS1548 Rating: 2014-03-12
Great Job ! Time Owned: 0 to 3 months.
What to say except "thanks!"...

I fit this small module in 20 minutes in the original mike of my FT-817 that i use for mobile QRP.

First test give around 6 dB more on the average signal received from the other side.
Modulation quality is still good.
Perfect !

Next step will be the RF Clipper Model PEP for external operation to fit between my FT-857 and my MD-100 at home.
N4AY Rating: 2013-12-17
Great audio-UNPROCESSED Time Owned: 6 to 12 months.
A bit of tweaking on the FT-857D menu items and the audio reports (with clipper turned off) have been very gratifying. No one believes I am on an 857.

Earlier 5-star review posted by N4AY on 2013-07-19

Audio processing is a passion of mine, although primarily in commercial broadcasting. When I acquired an 857D a couple of years ago I knew that it lacked many features of the higher-priced rigs. While the rig does offer limited microphone equalization, it did not offer any type of real speech processing. The rig does have a menu item to select processing, however it seems the circuit only contains amplification and no audio AGC or clipping. Previous experience with external devices on other rigs led me to begin the search for an RF type speech clipper for my little "Swiss Army Knife" radio.
When I ran across the eHam reviews on the DF4ZS clipper module when used with the FT-817, I decided to give it a shot with my 857D. The transaction with Joachim was perfect. It took 8 shipping days to arrive after ordering. Following the link to installation of the module in the MH-31, it took about 30 minutes to install. I elected to use the "TONE" switch on the back of the microphone to switch the clipper in and out, otherwise installation would have taken about 15 minutes. There were no problems found while installing.
When I fired up the rig I had to reduce the mic gain quite a bit, but after getting the ALC kicking in the right zone, I started making a few contacts. Simply put, this tiny little module makes the difference between being heard and understood and not being heard and understood. There are three adjustments on module, output level, clip depth and BFO frequency. Since I knew I was going to be tweaking, I drilled three holes in the microphone shell to allow adjustments. The stock settings were great but I found that by listening to a nearby SDR on the internet I could get exactly the sound I was looking for. Over the past couple of months I've experimented with this processor quite a bit and have come to the conclusion that this is the single greatest improvement one could make to any rig not equipped
with RF speech processing.
While designed for the Yaesu microphones, the module could easily be installed elsewhere in the microphone chain. Not having to carry another box when operating mobile or portable is definite advantage! Joachim has another interesting external processor containing a noise gate, audio compression and the RF clipper. I can't wait to get my hands on one...
G0VHT Rating: 2013-02-21
Excellent, works great! Time Owned: 0 to 3 months.
Like many hams, I was concerned with the apparent low audio output from the stock Yaesu microphone which is provided with the FT-817.

After much research and reading many reviews on this very web site (!) I elected to purchase the DF4ZS RF speech processor from Joachim. I was in 2 minds between this unit and the W4RT alternative however 'Waters and Stanton' were asking over £125 to do the same work which I think is a little over priced. The DZ4ZS unit cost less than £69 which included return postage - all in all much better value for your money.

I sent off my mic over to Germany as Joachim very kindly installs the unit for you (my eyes aren't as good as they used to be). Communications with Joachim was a pleasure, he kept me fully up to date and turn around time from posting here in the UK to receiving my mic back was less than 10 days - excellent service and very quick turn around.

The unit has worked superbly, I have not needed to adjust anything apart from turning down the FT-817 mic gain to compensate (max '40' on the SSB mic setting ensures a clean signal). Reports have been very favourable and the difference (using my dummy load with analogue wattmeter) is very easy to see when switching between a spare MH-31 mic and the DF4ZS converted unit.

All in all, I'm delighted, a fantastic customer service experience and a top notch RF processor to boot - if your are considering purchasing this unit, have no fear, it will be the best thing you ever did if like me you are a dedicated QRP SSB man!

Best 73's to all eham fans,

Paul - g0vht (UK)
HB9PL Rating: 2012-05-13
Excellent, inexpensive device! Time Owned: more than 12 months.
The „DF4ZS RF-Clipper“ is one of the smartest accessories in Amateur Radio. Its small size makes it unique to be built into almost any Hand mike. Contrary to other comparable products, the “DF4ZS RF-Clipper” has adjustments for

• frequency response
• output level, and
• clipping level.

These controls allow for individual settings according to the voice of the operator and the input characteristics of the equipment in use.

I own several of these goodies and have built them into YAESU MH-31 Hand mikes as well as a slim metal case with an 8-pin Mike Connector at the bottom. By means of specially tailored adaptor cables, I can use this homemade microphone with any rig that delivers around 5 VDC at the Mike connector of the rig (YAESU/ICOM) or up to 12 VDC by using a 78L06 fixed voltage regulator in the DC supply wire of the RF-Clipper board.

A device such as the “DF4ZS RF-Clipper” is not meant for “audiophiles”. It was designed by Joachim to enhance the intelligibility of voice signals generated by equipment of low and moderate power output capabilities. Although mainly on CW, I’m often told during SSB contacts, that my signal doesn’t even move the S-Meter from the noise floor, but the voice comes through fully and easily readable.

No further words needed.

Peter Langenegger, HB9PL
VK2BEN Rating: 2012-04-25
Great help for QRP ops Time Owned: 6 to 12 months.
After some correspondence with Joachim, he promptly sent the microphone kit in the mail. Very nice, personal service.

One thing to note: the instructions that came with the mic kit are the most up to date. The ones available online were not, which was a bit confusing at first. Make sure you are looking at the correct instructions come installation time!

Installation into the MH-31 mic is easy enough. A little bit of fiddling, and you can use the existing tone1/tone2 switch in the back of the mic to switch the processor in/out. This is an important point, as the processor uses battery power from the FT-817, and will continue to do so even after the radio is switched off! Of course, you can just ensure disconnection of the mic from the radio ;-)

Results: First thing to note is that the original dynamic mic element is replaced by Joachim's electret element. The resultant audio response is quite different and will require some audio and mic adjustments in your radio.

Switching in the processor, my receiving test partner experienced a signal improvement from an initial 41 to a 100% copy 53! Readability improved much, and pushed my signal well out of the surrounding mud. In my case, the empirically proven signal strength improvement was around the 6dB which was optimistically expected.

For QRP operation, being heard above the noise is a large part of the challenge, so better voice clarity was a great achievement; regardless of the actual signal strength. S-points are great, but readability can almost make all the difference.

I can recommend Joachim's product and customer service.

ZL4YY Rating: 2011-01-12
Great punch through QRM Time Owned: 0 to 3 months.
I received the Mini Type E for christmas. This miniature circuit is specially tailored for the FT-817 and should be a breeze to install in the hand mike. However I had to hook it to my FT-100 and Turner +3B desk mike. Once I understood the documentation, installation was quite straightforward. I had to fight some RF feedback coming from the +9V line of the FT-100 but easily solved the issue.
On the first evening I had four DX, all telling me I had a great audio. I was told that it was pleasant to hear (thanks to the Turner+3B) and coming through the european QRM with ease (something new).
Stock setting for the RF Clipper are perhaps conservative but fit my needs. Better intelligibility but keeping a natural voice.
Definitely a great deal if you don't need fancy bargraphs and front side buttons to play with and worsen your audio on the fly...
ON4CCU Rating: 2010-12-16
Significant difference Time Owned: 0 to 3 months.
I bought this processor recently to improve the average output power of my FT-817, which I felt was rather low.
Joachim offered to do the mod for me, at no extra charge. I sent him my microphone and got it back a little over a week later. Excellent service, original parts were in a small plastic bag should I ever wish to bring the thing back in its original state...
Does it work? Yes, there's a visible improvement in "talk power" (on the meter), it certainly makes a difference in QRP DX! A US station I was working last weekend on 15m reported that my signal was 54 (with 5w into a vertical), but I did sound much louder than his s-meter was indicating. Switching off the compressor brought my signal down to his noise level and very difficult to copy...
Just make sure you keep an eye on the mic gain...mine is at 40%, anything above doesn't provide any more signal improvement, but makes your audio sound harsh and aggressive.