I’ve owned a Kenwood TS-480 HX for quite a while now, but it was relegated to the shelf when I pulled the trigger on the purchase of a Flex 5000A several years back. Don’t get me wrong – the 480 is a GREAT rig, but the spectrum display provided by the Flex makes it the vastly superior radio – at least in my mind.
Recently, my wife and I planned a trip to the island of Eleuthera in The Bahamas. This is not your typical tourist island filled with shopping, casinos and frequented by cruise ships. This is a small, quiet island with many beaches (some of them are PINK) that are often all but deserted. MY kind of place – and my wife wholeheartedly agrees. We will certainly enjoy exploring, swimming and checking out the assortment of restaurants. At first, I wondered what we might do in the evenings. Sure – there will be more than one romantic stroll down a (hopefully) moon lit beach, but then what? I don’t get the sense that there is a lot of nightlife (not my thing anyway), and the idea of wasting my evenings watching TV was unappealing.
Then it hit me! I’ll bring my ham radio. 10 minutes of research and $35.00 later, and I was well on my way to having a Bahamian Ham radio license and call sign – C6AJB.
Like many Hams, I have a very hard time parting company with my toys – even when they have been replaced with new toys. My first rig – a TS440S was immediately chosen for the task, because the TS-480HX was waiting for me to get off of my lazy @ss, and complete the repairs I had started – QUITE a long time ago.
Side bar #1:
In my other posts, you’ll read about modifications I’ve performed on several types of radios – namely, removing the RS-232 interface hardware, and installing a USB replacement. Naturally, I could not resist performing this mod on my TS-480HX.
Note the mini USB in place of the DB-9 and the SDR dongle.
Given the RIDICULOUSLY small components this rig uses, this was the without question THE most challenging and difficult mod of its type that I’ve performed. After overcoming a few obstacles, I succeeded in getting rig control via pure USB – but there was a catch: The radio wouldn’t receive or transmit!
I had put a LOT of time and effort into that project, and by then I was frustrated and burned out. I was pretty sure that I knew where to point the finger of blame – the cheap and fragile white “Flat Flexible Cables” – a subject I am going to devote an entire post to at some point in the near future.
In recent years, these fragile cables have been the source of more thorns in my @ss than I care to tell you about. Anyway, I ordered replacements, but when they arrived, I was too burned out and discouraged to deal with it any more, so back on the shelf it went. Besides, I was having fun with the Flex, so there was no rush…
End, side bar #1.
I started to get the TS440S set up and ready to go for my mini, kinda sorta DXpedition, then I thought, “It sure would be nice to have the extra power and capabilities afforded by the TS-480HX”.
It was then I decided to get it back on the bench.
In less than 30 minutes, the replacement cables were installed, the radio completely reassembled and tested and everything was working well!
To say I was relieved, elated (and more than a little irritated) – is a classic understatement.
Some months ago, I began playing with these HDTV dongles that many have been pressing into service as Software Defined Radios. I found them to be serviceable – so long as you didn’t have very high expectations. These unit have their limitations – the most notable one being the MINIMUM reception frequency. Depending on the model, it will get down into the range of 20 – 40 MHZ. In order to receive frequencies LOWER than this, you need a model that has an “up converter” that shifts the lower frequencies upwards by 50 to 100 MHZ.
I bought a regular unit, and a model with an up converter circuit, but I wasn’t exactly impressed with either one. Lets not loose sight of the fact that we’re really NOT using these things for what they were actually designed to do, so you really should temper your expectations! The simple front end filter was all but worthless towards stopping strong, unwanted signals, and the SDR was easily overloaded. With the up converter model I had, you had to constantly monkey around with the gain trim pot in order to get anything resembling what I would call satisfactory results. You might get it to behave on any given band, but if you changed bands, you had to tweak it again.
Most modern HF radios include complex and effective RF front end filters that serve as “blinders” against all but the desired band of frequencies. There is usually one filter bank for each band. These filters offers VASTLY superior performance when compared to the simple LC filters on ANY of the RTL SDR’s.
Pressing a RTL SDR into service as a PAN ADAPTER makes much better sense than using it as a stand alone receiver – on two fronts: 1) you get the benefit of the superior RF front end filtration afforded by your HF radio, and 2) By tapping into your HF radios’ first I.F. output, you eliminate the NEED for an up converter (normally required to receive HF) , because the radios 1st mixer / I.F. circuit – IS – the up converter.
There are other benefits that will become clear, later.
End sidebar #2.
The TS-480 1st I.F. frequency runs at 73.095 – well above the minimum frequency of any RTL SDR dongles. I decided to tap into that signal, present it to the antenna connection of the RTL SDR, then tune the SDR to that frequency, and I should be able to see – and hear QSO’s above and below whatever frequency the 480 was tuned to.
After reviewing the TS-480 service manual, I was pleased and surprised to discover that Kenwood was nice enough to include a simple 2 pin connector on the RF board (CN152) that provides a sample of the first I.F. signal – before – it goes into the roofing filter.
This should be easy!
I started by sourcing a cable with a suitable 2 pin connector (see the photo – above). This is fairly common connector – and it didn’t take long before I found a junk donor board that had one. I figured it would be fairly easy to “rig” something – if push came to shove. Carefully soldering the leads from a short length of RG-174 directly to the pins would be perfectly acceptable.
After removing the cable from the donor board, I pushed aside the screen material and routed the end of the cable out through one of the vent holes on the 480. I opened up one of my RTL SDR dongles, unsoldered and removed its RF connector, then dressed the bitter end of the cable, and soldered its leads directly to the board where the connector once attached. I think that’s a much better option than to trying to fight an odd ball connector onto the tiny RG-174 sized coax. This plan seems to have worked out well.
The cable is secured to the shield with a wire tie in order to prevent accidental disconnection.
After firing up my favorite SDR software (HDSDR), I spent a considerable bit of time configuring it. Though it’s not quite up to par with my Flex 5000A, I think it’s safe to say the results are pretty respectable, And you DAMN sure cant beat the price!
Judge for yourself…
Though I don’t hear any evidence of signal degradation in the 480 with the addition of this mod, I’m still considering adding a buffer amp – perhaps with just a little gain – in order to achieve increased isolation and give the SDR a slightly hotter signal.
Clifton Labs has a nice offering – HERE.
Finally – for now – this process should be possible on most ANY make and model of modern Ham radio equipment. It should also work with VHF and UHF gear too.
Stay tuned for part 2 when I chronicle the set up process.
BTW – the contact form on this website is broken. Direct any questions to steve – at – marine electronics repair d ot co m.
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