3.4 GHz Transverter Conversion (3.5 GHz WiFi transceiver)

[VK3ALB]

Hi Everyone,

3.4GHz transverter in action

Here's a simple 3.4GHz transverter made from a surplus 3.5GHz WiFi transceiver.

• Works with any low power 70cm transceiver or handheld.
• Runs from 13.8V DC and puts out around 750mW on TX.
• Perfect for mobile or rover operation.
• An excellent weekend project.
• No complicated alignment routine.
• Conversion parts can be sourced locally.
• Supplied with detailed conversion instructions.

The conversion requires the replacement of a ceramic filter as well as changes to some SMD components. You will also have to make a couple of simple PC boards to handle PTT control and RF switching.

Three complete transceivers are required to make two functional transverters. We recommended that two people get together and modify two panels sharing a third panel to complete the conversions.

How Much?

Panels are only sold in lots of three for $50 – buy two get one free.

Please note - these panels have been taken out of service after years of exposure to the elements - they are not new. They are weather worn and as you would expect will be dirty and have evidence of bird droppings. Each unit is inspected externally for physical damage, given a quick clean then a quick power up test to ensure they are alive.

What to know more? Visit http://www.vk3atl.org for more information.

[VK4TIM]

So for those of us who live outside VK3, are you able to pop them in a box and Australia post them for the appropriate amount?
To VK4 shouldn't cost more than about $20?

I'd be interested in a couple.

[VK5PJ]

Tim

So for those of us who live outside VK3, are you able to pop them in a box and Australia post them for the appropriate amount?
To VK4 shouldn't cost more than about $20?
I'd be interested in a couple.

You may want to talk to some of the VK4's going to Gipps tech in a few weeks time, they could carry back as hand luggage ?

Peter.

[VK4EA]

I already have set aside room in my bags for some units, Tim, consider going to Gippstech! Or talk to me real nice

Sent from my SM-T805 using Tapatalk

[VK2KYP]

Hi Will the boards be available at Gippstech, if so I would like to reserve a set?

Thank you

73 Gary vk2kyp

[VK3ALB]

Hi Everyone,

Yes I will bring panels to Gippstech however to avoid disappointment please make sure you email me directly and place your orders. I will respond to each request and confirm your order.

[VK3ALB]

Hi Everyone,

Today I took a modified panel into the field to see how it would go. There weren't many out there but I did manage contacts with four stations and failed on two others.

Twice with VK3UHF @ 37km easy copy S9
Once with VK3NW/P @ 44km easy copy S9
Twice with VK3KQ/P @ 95km easy copy S7
VK3QI @ 117km nothing heard either way
VK3MY @ 139km nothing heard either way
Once with VK3APW/P @ 168km really challenging contact but we made it - 4x1 I think a CW or digital contact would have been much easier.

Conditions were pretty flat on most bands but I'm pleased with the results. Looking forward to better conditions next FD.

3.4GHz panel on mast

[VK1JA]

Hi Lou,

Considering the power output and the band, that's pretty impressive - well done !

[VK5ZT]

Hi all

Kicking this can a bit further down the road......here is the initial results of my investigation into the ATmega8 processor functions in the TRI3500 3.4 GHz transverters. Hopefully will have the complete picture soon...

The ATmega8 was used in early Arduinos. I think, and is pin for pin with the ATmega328 but there are some internal differences.

ATmega in TRI3500.xls

ATmega in TRI3500

(55.5 KiB) Downloaded 1007 times

My thoughts were to either reprogram or replace the ATmega8 to allow my own version of control of the transverter. I do not want to move away from the Arduino development environment so would be looking the replace the current software with Arduino based version. Investigations indicate that both reprogramming and replacement are likely viable options so I may try both, just for the hell of it.... Fitting a 16 MHz Atmega would need the crystal and caps...but the TRI3500 board already has provision for these!!!

Why do it at all???

1. Because its there!
2. Flexibility in frequencies used for IF etc. We may need to move in the future.
3. Using the micro to control the relays, slightly reducing parts count/effort.
4. Using the spare PLL2 to create a beaconing mode. Transverter could be run as a beacon without IF radio.
5. Potential to use PLL2 as an LO to add a second down conversion to 2 meters (TX side already has unused mixer, only need RX mixer). This approach may be better than moving the main oscillator for filtering reasons. Note also that the PLLs have discrete VCOs that may need to be altered.
6, Use micro to monitor critical internal voltages....it may already do this but I haven't found out where yet!!

The PLLs are nothing special and fairly straightforward to program (easier that 4133) and have wide range BUT use external VCOs.

I will be modding 2 units 'by the book' just to prove they work, then reprogramming/modding one as a test bed for the changes.

I am interested if anyone has any thoughts/ideas or may be interested in my results........

Cheers Tim VK5ZT

[VK3ALB]

Hi Tim,

That's very encouraging news and I'm sure we'll all be watching with interest. It's one of the things we thought would help boost its appeal but we're a bit lacking on micro skills this way. Sadly, we have not found the circuits for the panels but if anyone does manage to find them I'm sure everyone who has purchased the panels will be interested to see them.

[VK3HZ]

Hi Tim,

Arduino is just a state of mind - for the ATMega. There is a bootloader for the ATMega8 so it could be used. Replacing it with a 328 would be a hassle and could result in damage to the board.

The 3 CPU pins that go to PCB pads (15, 16 and 17) are for in-circuit programming of the chip (along with Reset).

Looks like the CPU mostly deals with programing the PLL's although you might need to trace those few analog inputs (if that's what they are).
A longshot, but maybe the manufacturer hasn't set the memory Lock bits and the original firmware can be read.

I'm looking forward to getting units myself.

Regards,
Dave
VK3HZ

[VK5ZT]

Hi David

I figured those other pins were for programming and yes, its a guess that the unidentified pins may be analogue. I do know they do not appear to turn up as direct connections to any of the ICs etc. so assumed they are probably connected via resisters to monitor voltages (another guess). I am pretty sure there will be a line to enable Tx but have not found it yet but then what I have found has only been the result of an hour or two of poking around and noting results.

What was in that table was established with a meter on a board with all shields removed. The next step is to power the board without the micro and see whats there... I don't think the micro does much more than set up the PLLs and then watch the status of things (signal detection, lock detection. tx watchdog etc..) all of which can be reprogrammed if so inclined so I don't much care about the original code. I only just taught myself C/C++ about 8 months ago and used Arduinos for all my experiments so prefer that world. I am disinclined (and too lazy) to have to deal with other programming interfaces, development environments, compilers etc etc...Its enough keeping track of all my Picaxe/Maximite/Duinomite projects as well!!!

Hopefully more will be revealed this weekend and the first experimental board tested.....

Cheers Tim VK5ZT

[VK2JDS]

Over the last few days I have got one of the panel transverters operational following the instructions provided by Lou and the geelong club pdf.
It works really well and I encourage you to have a go and get yours going.
I chose to bypass both the tx and rx duplexer filters and mounted my TR relay pcb near the hole in the pcb where the antenna coax comes through just by soldering its small pcb to the mainboard.
The dc switching and IF switching boards were easy to make using a dremel tool and i used 2 RF relays bought from Mark vk5eme at his Minikits website.
If you bought 3 units then you can use the spare one you took the filters out of as a signal generator just by linking over where the tx filters used to be. Alternatively use a uhf handheld tuned to eighth harmonic. 425 MHz. This will assist in peaking the receiver, the transmitter can be monitored for output using a current meter on the 12v supply cable.
To key up the transverter a simple mod to the ft817 will allow it to work via the rear panel SO239. No mucking about with the accessory sockets etc, and i will be using the same way to key up my other transverters.

Pics to follow
73 Dave vk2jds

[VK2JDS]

This pic shows the main pcb with the vk5eme relay mounted near the tx and rx duplexer filters. The 2 pcbs under the main board are what i have just constructed.
They use a w1ghz relay pcb (the vk5eme would be fine here too) and dremel cut pcb pads with soldered in vias to the groundplane underside. The relay is an omron G6Y-1 which does the IF switching to the main board. The pcb material is double sided fibreglass from wyong field day , ebay etc.
Its all easy to make as you can see.
The 12 volt relays are no longer available ( why ???) so these are 5 volt ones. To solve the voltage problem i bought a packet of 78L05 regs from ebay for peanuts and put one at every relay. Use 0.1Uf caps from input and output to ground pin using smd chip parts or whatever you have handy. SMD components are so cheap and plentiful these days.They switch fast enough. I mounted them on a vertically standing pcb from w1ghz which costs 3 dollars. The relays are 8 dollars.
I will soon have 2 more transverters functional for some range tests once these boards are installed.

work progressing, if anyone else is building theirs please post a reply here
73 Dave vk2jds

[VK2ZRH]

Good work, Dave.

Do you plan to use the on-board panel antenna, or are you gonna try to take one and dish-it-up.

[VK2JDS]

Hi Roger,
One of the boards will definately go up on a big dish here. The septum is already mounted, with a G4DDK lna and a transco relay.
Sun noise will be interesting. The snow and sleet has hampered progress on outside jobs, so building up the pcbs yesterday was a good inside job to do.
Will post up what results i get over the next weeks, unfortunately we missed last weekends 3.4Ghz EME activities.
Phil vk4cdi and Charlie vk3nx are both operational on 9cm moonbounce.
Some completed units will go to sydney, i will keep one for portable and another for homestation use.
73 Dave vk2jds

[VK2JDS]

tomorrow sun noise, but for now :

Some experiments on the receiver side of the transverter
In order to save wrecking a whole unit by gutting its pcb for filters i have applied some thought to simple no cost replacement devices.
What about a couple of shortcircuited stubs made from rg174 or 141 hard line linked by a half wavelength ?
Test 1 was to get a gutted board, do the IF mod and the coil change on the post mixer pcb. I set up the 492 spectrum analyser on the output of the board where it goes to the ft817 to monitor results.
I linked over the pcb pads where the receiver 3.4GHz filter would have been and then swept the sig gen from 3.39 to 3.41 and tuned the capacitors on the small pcb. (after doing the coil replacement mod)
With that peaked at 3400 next was to observe the signal level change as i applied a shorted quarterwave stub of rg174 16mm long at the filter position on the mainboard.
No change
this is good
next I tested a shorted stub 18mm long and the signal dropped by several dB on the spec an.
very good. so 16mm pieces will make a reasonable filter. whats better than one stub? 2 stubs separated by a half wavelength.
Halfwave is same velocity factor cable twice the stub length. but, for the time being i just set 2 stubs on each pcb pad where the filter would have been , then linked the pads with a piece of wire. It works well !
300/3400 , divided by 4, multiplied by close to 0.71 velocity factor = about 16 mm

photo shows the 2 stubs with the linking wire on the position where the receiver filter normally goes

To make the stubs I cut 20mm of rg174 i think it is.
cut off the plastic outer from both ends back 5mm . fold the braid back and cut 2mm of the insulation off from the inner of one end to expose the centre conductor.
Now fold the braid back over the trimmed and tinned inner , twist and solder.
Measure 16mm from where you think the inner is soldered to the braid and cut off the outer plastic of the cable. this is your length reference.
On the end getting soldered to the pcb fold the braid back to the plastic and twist so it makes 2 sides. , The inner will stick out 3mm or so, trim back and remove 1mm of insulation around the core.
Make 2 of these pieces and solder them on like in the photo and add a jumper link or make a half wavelength using same principle to link the 2 pads.

Thats the receiver sorted out, next is the transmitter.....

73 Dave vk2jds

[VK3XL]

To key up the transverter a simple mod to the ft817 will allow it to work via the rear panel SO239. No mucking about with the accessory sockets etc, and i will be using the same way to key up my other transverters.

73 Dave vk2jds

so what is the simple mod to the FT817?

[VK2JDS]

http://www.kuhne-electronic.de/en/servi ... ducts.html

There are other descriptions using the front socket rather than the back.
I just googled ft817 transverter mod.

The transmit filters are made and soldered in place on the gutted pcb. Now it needs the rf and dc control pcb made.
73 Dave

[VK3XL]

Thanks Dave. I tried google but didnt come up with any links that helped. The one you linked in the above post was most helpful.