VK3XDK 2.4GHz Transverter project by VK4GHZ

[VK4GHZ]

For sake of variety, here is another version of the code that has a few more comments, explaining its operation.

Thanks for sharing Dave, looks great.
Although I have a HP32S RPN calculator (which easily converts base 10 decimal to hexadecimal), I like the way you can simply enter desired frequencies in straight MHz.
This makes it very user-friendly to setup.

I'll definitely give this a go tomorrow, and I am sure others will try this version too.

Using the PLL board as a signal generator, with maybe a rotary switch on the front panel to select the O/P Freq, this is ideal.

[VK4GHZ]

The VK3HZ code works a treat!
No need to power down to change frequencies now.

With email received from others, some PLL Boards out there may not be setup to generate 1970MHz as-is.
If your PLL is not locking at 1970MHz, this may involve a tweak to the small printed inductor.
The inductance is reduced by placing a solder short across it.
A lower inductance will raise the center of frequency lock.

(I ordered my PLL Board along with the 2.4GHz transverter kit, so VK3XDK may have added the inductor short specifically to suit operation at 1970MHz.)


Above: Inductor details. Note solder short across IC pins 7 & 8.

My PLL Board does not lock at the lowest standard frequency of 1008MHz, and I haven't moved the inductor short to try and obtain this, as it is not required for the 2.4G transverter anyway.

[VK2GG]

To Adam, Peter, Steve, Rob, and others,
enjoyed the artivle Adam, along with the other tips from others,
good luck with the final product, I look forward to working you on 2.4!!
cheers,
Dan VK2GG

[VK3HZ]

Adam,

Just out of interest, if you want a PLL Lock Detect indicator, the pad at the right of your picture above (under the "here)") is the AUXOUT pin from the chip and is configured by the software to be a Lock Detect output. Both versions of software do this.

The output can only source/sink about 0.5 mA, so a buffering FET/transistor would be needed to drive an LED.

Regards,
Dave.

[VK3HZ]

Here's a final-final version of the code. I've incorporated support for the RF2 output. Now if you put say 432 in the table, 432 MHz will come out RF2 - providing you have the right value inductor, of course.

[VK4GHZ]

Here's a final-final version of the code.

"Final"?
That's a big call, Dave!

Graham, VK3XDK, has acknowledged there is a small problem with the 1900-2100 Multiplier overlay and you may find that a few parts are missing from the multiplier kit.
Missing in mine were: 2 x 16pF caps, and 3 x 16R resistors.
Graham is posting out the missing parts.
Please note: there is a new overlay (with value changes) for the 1900-2100 Multiplier board, as of today.
If you are affected, please contact Graham directly, and I am sure he will look after you.

My eyes are finding the overlays a bit difficult to read, so I re-edit them with Photoshop for my own purposes.
Note: This is not an official document, but I am simply sharing my own version with others.
(I believe the VK9NA web site is meant to be the official source of all documents)

Updated 8/2/11 1900-2100 Multiplier board.
Note some value changes.

I have also edited the supplied word doc for my own purposes.
Again, this is not an official document, but if you find it useful, go ahead and use it.

2.4 Transverter_VK4CP edit.doc

VK4CP 2.4G Transverter doc re-edit

(418.5 KiB) Downloaded 613 times

[VK4ADC]

Adam

Following your posting of the DOC edit file, I went web searching to see how a shift to 2304 would go ( see topic viewtopic.php?f=40&t=585 ). I researched the Murata SAW ( 2441.5 MHz CF ) that is used in the 3XDK design and there doesn't seem to be any alternate filter available that covers the 2.3 GHz segment from Murata, EPCOS, etc.. The next series of SAWs below 2441/2450 seem to be centred around 2140 and only have 85-odd MHz total bandwidth so fall short of the 2304 passband target.

I realise that this forum topic is about a 2.4 GHz transverter project - as against a 2.3 or 2.3/2.4 - but the design, while simple, doesn't provide for any future moves in band segments. My initial thoughts were that I would mirror your arrangements to get going on this part of the spectrum but with my research tonight into readily available SAW filters, maybe not. Hairpin tuned lines on a PCB may not be easy to move the 100 MHz but by cunning PCB layout coupled with some line shorting/shortening segments, that should be possible, certainly more-so than shifting this one down.

I will be interested to see how it all works out.

[VK4GHZ]

... but the design, while simple, doesn't provide for any future moves in band segments...

Doug, yes I know!
It was a consideration as to whether I bother spending $$$$ on 13cm or not.

I'm a late-comer to 13cm, and as I found out after the fact, the issue about moving all VK terrestrial work down to 2300Mhz has been discussed on the Forum here before, and elsewhere.
It seems nobody can come to an agreement, and/or is willing to do anything about it.
We are all too short-sighted and stubborn for our own good.
This is really sad, as we would all get better long-term use out of our gear if it had dual use, ie; domestic with an easy EME capable upgrade path.

Anyway, that is another topic.

[VK4GHZ]

Catching up on a few pictures of recent progress...

Both the 1900-2100 Multiplier and 2.4GHz transverter PCBs were glued down to their respective aluminium base plates using silver epoxy.
Only a thin smear is required, so the silver epoxy kit will do many boards.


Above: PCBs fixed to base plate using silver epoxy. A nice flat bond is not hard to achieve.

The CW2400 silver epoxy data sheet mentions that better continuity and hardness properties can be achieved if the epoxy is heated up whilst curing (compared to 25° room temp).
This can be done by giving the base plate side a blast with the heatgun all over, and letting it cool naturally.



Above: Look Ma! No screws. DC continuity check between PCB top side and base plate.
(BTW, multimeter reads 0.5 ohm when the two probes touch each other directly - time for a new MM battery!)

Isopropyl Alcohol (IPA) cleaner is very effective for cleaning the aluminium base plate in the first place, and any silver epoxy residue away.


Above: This 100mL IPA spray pack was obtained from Bunnings (about $7), but I later discovered Jaycar also sell IPA in two sizes (and it's cheaper at Jaycar)

Remember this: It is much easier to mount the SMA connectors before any parts are fitted to the boards.

Instead of using self tappers, yuk, I used 2.5mm screws to mount the connectors to the base plate.
Position the connector, mark only one hole for now, then in a drill press, drill a 2mm hole, then tap it with the M2.5 tap.
(Do not attempt to use a hand drill with small drill bits - that will end in tears!)
Mount the connector with this first screw, then drill through the middle of other connector hole (in situ) to ensure an accurate second hole alignment.
(There is very little wiggle room when using M2.5 hardware)



Above: SMA connectors fixed to base plates with 2.5mm screws in tapped holes.

Don't forget to use some "soft jaws" on the PCB side of the drill vice.

[ZL4PLM]

your doing a fine Job Andy

nice to see - watching with interest

My mini kits interface arrived sat so thats now built and ready and my 3w PA from DEM arrives soon I hope

I will be ready with my demo 10g gear for the wellington expo

this is actually a second setup for /P use - my other gear is more upmarket - a full locked DB6NT with 12w PA

Im v interested to hear how this is on air and how it performs

73 Simon ZL4PLM

[VK3XDK]

Very nice job, Adam!! You sure are doing it properly

Just a small comment for now.
To drill the holes for the sma's I now use a dremmel with its drill chuck accessory. I drill by hand even though ive got a drill press.
"Tapping" or "drilling lube" is needed as the most likely disaster would be if the drill breaks in the hole (caused by the swarf not exiting the hole and binding up the drill)
A very fast speed is suitable for aluminum (I use flat out!) And removes the metal quickly without the need of much drilling pressure.
The drill should be only a little bit smaller in diameter then the outer edge for the screws that have been chosen. (ie for a 1.2mm self tapping screw, a drill of 1mm)
For tapping, use a tapping chart OR With metric, the size is measured on the outside of the thread (with a screw). Subtract the thread pitch for drill size (ie a metric 5mm x 0.5(pitch) screw would require a 4.5mm drill hole (prior to tapping))
Metric is very easy.

hope this helps, Graham VK3XDK

[VK4GHZ]

Ok, I have this running on the shack bench now!

Here's a quick look at the beast. Shack is a mess, like a bomb went off, so no wide shots.


Above: Front view. At left, RS232 port from Thunderbolt going to laptop. Band select on right, with LED indicators for mode.
Fitting an LCD display, where the DB9 connector is, will ultimately replace the need for an external laptop to interogate the Thunderbolt status.


Above: Looking into rear corner. Thunderbolt, DC input wiring and fuse, along with GPS antenna BNC, and 2 (of 4) 10MHz O/P BNCs.
At right you can see the ANT port for the [future] 3.4GHz system, along with the control cable (a CB 4-pin microphone plug/socket) coming from the 817.


Above: Looking to right. VK3XDK 1900-2100 multipler board in front, with 2.4G transverter board behind that, and a Spectrian 30W PA mounted on the enclosure side.
In addition to the Spectrian base plate, I have mounted the Spectrian onto another 6mm aluminium plate for extra heatsinking capability.
VK3XDK PLL board bolted on top of transverter board, sitting horizontal.
VK4CP Sequencer board at front.


Above: Looking to rear panel. Tohtsu coax relay from FT817 for input switching between 2.4G system and [future] 3.4G system.
Output SMA relay for T/R switching between XDK transverter RX path and the Spectrian amp O/P.
All the coax is RG-316 teflon, which is very easy to work with.
At 2.4Ghz and lower, the short runs of coax mean any loss is insignificant. There is no need for hardline or semi-rigid cable.
(The only hardline used is the 086 stuff that came with the Spectrian PA, which is terminated with SMA connectors)

With the FT-817 set to medium power (2.5W out), I get +2.5dBm out of my sequencer, going into the transverter TX IF i/p
Coming out of the VK3XDK 2.4G transverter board is +21dBm - exactly on spec.


Listening to myself on the IC-R1500 directly on 2403.100MHz FM, it sounds nice and clean.

Have you measured the input SWR on transmit as yet ?

Input SWR is 2.3:1.

A couple of really well produced pdfs for your recent projects..................much appreciated, thank you.

Thanks
Glad any information is useful, it makes the documentation process worthwhile then.

Where did you obtain the 150 ohm smd 1 watt(?) resistors?

Paul, these resistors were sourced from RS.
http://australia.rs-online.com/web/sear ... &R=2240294
In fact, I purchased quite a bit of stuff from RS.
Their online ordering, and free delivery make it so easy... so I couldn't be bothered with Rockby etc.

[VK4GHZ]

Quite happy with the Spectrian power amplifier too.

Exactly as PyroJoe says in his eBay listing, 35dB of gain can be expected with these 30W boards.


Above: Spectrian temporarily removed from transverter enclosure for test.

The VK3XDK 2.4GHz transverter board is delivering +21dBm out.
I feed this via an SMA attenuator (nominally 12dB) and +9.57dBm is being fed into the Spectrian PA.
The Spectrian saturates at any more than +10dBm in, so there is little to be gained exceeding that drive level.

As I cannot read above +30dBm directly with the spec an, I use a HP 779D Directional Coupler (obtained off eBay).
The coupling port was measured being -21.0dB at 2.4GHz.
The coupler's through port was terminated with a Weinschel DC-8.5GHz 50W termination (another goodie picked up from eBay).



Output is 23.4dBm as measured + 21dB via coupling port = +44.4dBm being delivered out of the Spectrian.
This translates to 27.5W, so happy with that.

At 13.8V, this Class-A amp draws around 10A delivering this output.
These Spectrian boards are not known for their efficiency, but who cares, they are plug and play, and work as advertised.
They are a relatively cheap and easy way to generate some grunt on 13cm.

Quiescent current is just under 1A in idle.

I'm glad I bolted the Spectrian base onto another (larger) 6mm aluminium plate.
It's quite hot, but all my testing has been with FM, and I don't expect heat to ever be an issue with the low SSB (or CW) TX duty cycle in Field Day use.

Incidentally, the second harmonic at 4.8GHz sits at -11dBm (80uW).

[VK4GHZ]

And rear panel.

Enclosure is a 3RU subrack.
With this height, and as you have seen above, the VK3XDK boards, Thunderbolt, and Spectrian can all mount vertically.
At a pinch, you might even fit three systems in a case like this, (2.4 + 3.4 +5.7), leaving a 10G system to be mounted in a compact box of it's own as close to the dish feed as possible.



The rear panel already had some cutouts in it, most of which were filled with connectors.
My sincere thanks go to Steve VK2XDE for helping me with this enclosure.

When not being used on Field Day, this can sit in the shack 19" rack, and the internal Thunderbolt can be used as the main station GPSDO.
I was going to build up a second GPSDO system solely for shack use... but why waste money when I already have one sitting idle for most of the year!

[VK4GHZ]

It works!


Above: VK4RBB 2403.440 beacon receive test, setup out the front where terrain slopes off rapidly towards the north & east.

I was wondering what I could use to mount the transverter kit on.
Whilst thinking of buying one of those fold-up camp table & bench seat thingos... I noticed the Black & Decker Workmate in the garage just sitting there.


Above: VK4RBB received from the other side of town. VK4RBB on 2403 runs 2W into a slotted waveguide.


Later that evening, a QSO with VK4KZR, over a less than ideal path cutting through Mt Coot-tha (where the Brisbane TV and FM broadcast TXes are located).
At the red cross HASL is 120m, so that didn't help. My signal was still 5x5 at Rod's place.


Above: Gridpack mounted on heavy duty [still] camera tripod with quick release plate on ball mount.
Handy for tilting polarization around to vertical, if ever required.

I might even use this same tripod with another quick release mount on the 10GHz dish, for a quick swap over.
Sand bag the tripod legs with some weight, so it isn't disturbed during the antenna change over... that way the dish is prealigned for 10G after a 2.4G QSO.

[ZL1TPH]

I’m suitable impressed with the construction Adam and it is a credit to you. It is easy to knock up the boards etc but the knack in construction is to finish the end product. And that requires a box to place it in to begin with. Once you have the box the real thought goes into putting it all together.

You have shown that.

I like the idea of room for both 2.4 and 3.4 GHz. The 9 cm or 3.4 GHz band is often the forgotten band but I believe worth pushing ahead. Both of those bands go together like 5.7 and 10 GHz so to speak.

In my opinion there is nothing like having output power meters installed on the front panel. Use 30 dB couplers as not to reduce TX output power and to show to yourself that you are transmitting.

I have had a few shouting matches over the air to others that can hear me and they can’t be heard at my end because they are not sure if their TX is working due to dying batteries in the field and the end result is they were not.

Cheers, Steve

[VK4GHZ]

...In my opinion there is nothing like having output power meters installed on the front panel. Use 30 dB couplers as not to reduce TX output power and to show to yourself that you are transmitting.

Steve, to have some confidence metering is an excellent idea.

Rather than directional couplers for both the 2.4 and 3.4 systems (and the rectifiers etc to create a DC voltage that can be measured), what about simply monitoring the main 13.8V DC current draw?

We know a Thunderbolt draws 1A initially, reducing down to 500mA
We know the Spectrian draws about 1A in standby
The actual transverter and multiplier boards don't draw that much (haven't actually measured it, but you know what I mean).
Anything above that, when in TX mode, must be the PA current.

Any thoughts by anyone on this simple approach?

[VK3QI]

Agreed Adam,

There is nothing more satisfying than watching a DC meter kick up and down with the voice peaks on SSB (or CW). My 2.4 Ghz Spectrian draws 40 amps plus at 27 volts and after a while you get to know just how the meter movement responds to your voice peaks!

Congratulations on an excellent documentation (blog) of your project with some very detailed photographs.

One point to note - on the Spectrian driver board there is a small pot that can be used to control the level of drive signal. Being designed for exchange work, the original design was specified for 0 dBm drive.

You may find it more conveneient to use the pot control rather than the SMA in-line attenuator.

27 watts out is just about right for 2403 Mhz, given that they are optimised for 2350Mhz

Cheers

Peter VK3QI

[VK4GHZ]

Ok, after some real world operating in the Winter VHF/UHF Field Day, I have made some refinements.

A 10A DC ammeter from Jaycar has been added to the front panel.
(Now I really do wish I had mounted that Thunderbolt DB9 on the rear panel!)
Monitoring the DC current is much easier (and a lot cheaper) to implement than directional couplers and rectifiers etc to measure absolute RF power output.



At start up I can see about 1.2A, 1A to the Thunderbolt, and about 200mA for the transverter, multiplier and PLL boards.
(When the Thunderbolt's internal OCXO heater cycles off, the current falls by about 500mA)

When TXing on 2.4 GHz, I see around 8A during idle, as the Spectrian amplifier is class-A... and when I modulate, ohh the joy of seeing the meter bang up against the end stop!

Now, as the Spectrian always draws about 6-7A in idle (I did mention it's class-A!), I have added an automotive horn relay, also from Jaycar, to switch the +13.8V to it during TX only.


Above: 30A rated relay is easy to mount with a single hole, and is activated on 2.4G TX only, so power is only applied to the Spectrian during TX.

Now, there is no wasted power during receive, and because of this, the amp runs cooler, so dissipating heat becomes less of a problem.
The Spectrian PA board does actually have a "TX enable" pin, (which is taken low on TX), but does not cut off the idle current during RX.
(A bit dumb, but that's the way it seems to work)

My participation in the Winter Field Day was limited to Sunday morning only, and the FT-817 was used on and off for the four hours using it's internal battery.
For longer periods of activity, an external DC supply will be required.
It seems silly running a separate DC lead back to the PSU for the FT-817, when there is a DC lead running to the transverter anyway.


Above: A pair of banana sockets were added, to provide a 12V/13.8V feed for the FT-817.

Whilst adding banana plugs to the DC lead that is supplied with the FT-817, I also added an in-line 3AG fuse... a serious omission by Yaesu.


Ohh, and the 3.4 GHz system was fitted in the box as well, but that will be another topic.

[VK4FLR]

Guys -Dumb question - Can anyone give me a part number or point to where to purchase those 2 pin polarized DC PC board header connectors I see everyone using on the various boards to supply the 8V/12v.... I've hunted for hrs with no results including RS&JC - I would need the pins you solder onto the PC board as well as the cable connector ?
73
Frank