FT897 DATA interface and PTT

Gavin (M1BXF) and I were playing with JT65 last night and my FT897 has a really nice data interface but no easy way to PTT using JT65 data mode....

So bodge time, took the xggcomms audio side of the Yaesu FT-Cable-1-Kit-USB 

Gavin added a simple PTT to pin 3 on the data interface by splicing in a cable to the data plug on the above interface.

The interface 'could' have used a USB interface but we didn't have one to hand so used a normal 9 pin come port and the RTS line and a usb/serial interface.

On a 9 pin com port he added just the top part of this.

Now the FT897 will ptt with JT65.

It is one annoyance with the radio that the data port will not vox ptt on tx audio.

455KHz filter from 455KHz ceramic resonators

Anyone pondering a 455KHz filter for their nice shiny yaesuicomkenwood rig... well I have played about with building a 455KHz filter using cheap ceramic resonators just like crystals in a ladder filter.

The idea is certainly is not new. G3VA, LA8AK, VK5BR and G3JIR wrote about it a while back. TT covered it numerous times the last one I have was from May 2003. There was a in interesting test rig diagram showing how to measure the series resonant frequency of ceramic resonators.

On one side you have a signal generator and a digital frequency counter, feed the signal into a resistance network, to which is connected one side of the ceramic resonator, then an identical resistance network feeds the output into a an RF mV meter. An Oscilloscope monitors across the ceramic resonator. At the series resonance frequency the signal will change.

I also used a couple of the options from http://w7zoi.net/xtal_methods/xtal_methods.html

Anyway starting with the batch of resonators I have I measured a handful until I found some that were about the same value. 

The why is because I am about to do a trip and neither my FT817 or FT897 has a SSB filter in either rig. How difficult can it be to make one instead of parting with cash? (I started to write this before I had a little issue with the FT817!)

So I have a few CSB455E (yellow) 455KHz ceramic oscillators and thought I'd make up a simple ladder to see what is possible.  These are the results following the methods laid out here http://users.tpg.com.au/users/ldbutler/LadderFilter.htm using a ceramic resonator instead of a crystal.

If I use the G3JIR values (source Radcom TT) in all sort of programs seemed to ring true.

Series frequency 442kHz

Parallel frequency 456kHz

Series Capacitance c18pF

Parallel Capacitance c280pF

I measured:

Series frequency 443kHz

Parallel frequency 457kHz

Series Capacitance c17pF

Parallel Capacitance c276pF

R = 10.3 Ohms

Ls = 7.92 mH

Circuits and images of the filters:

2 units (aka 2 pole)

4 units (aka 4 pole)

6 units (aka 6 pole)

Images of the outputs:

I also tried these options http://lea.hamradio.si/~s57nan/ham_radio/xtl_fltr/xtl_fltr.html

The math gets a bit fun if you want to calculate what is going on but I go started off doing the plug it in and measure method and I used a spectrum analyser and a VNA. 

The ceramic resonators I picked up from ebay at the princely sum of 6.99USD for 50 of them including postage costs.

The capacitors were from the junk box.

Probably too late for this trip so will do it when I return but I will make up a small board with SMT caps to mirror the commercial Collins filters and fit into the rig.

Bijol Islands AF-060

CANCELLED NO PERMISSION TO LAND ON AF060

It is possible I might be QRV one day from Bijol Islands AF-060 which are off the coast of The Gambia during my stay with the same C5 call sign 22nd - 29th August.

I will have the same station as AF-045 and will be SSB only!

Highly likely will be on 20m or 17m and probably QRP.

Watch this post or blog to find out day I will activate the island.

For those interested in more than just the IOTA... I'll take some photos.

Bijal Islands,Bijol Islands
Gambia » Western
islands
N 13° 23' 7'' W 16° 49' 1''
13.38528 / -16.81694

Bijol Island formed part of Tanji (Karinti) bird reserve. It covers an area of 6.12 square km and managed by the Department of Parks and Wildlife Management of The Gambia. This marine habitat is the main offshore island that provides home for migratory bird species, and it takes advantage of the absence of human disturbance. There is also an abundance of fish species in those waters. The island is covered with low growing saline-tolerant vegetation such as the beach morning glory, and baobab trees.There are many different bird species such as Royal tern, Caspian tern, Cirey headed gull, Whimbrel long tail, Comoron, Little warbler.

I might be lucky as the island provides shelter for resting of the marine turtle and other sea mammals.

A bird monitoring program has been conducted in the island by Professor John High, a British national residing in The Gambia. This monitoring has played a significant part in capacity building of the protection of conservation of Avi-Fauna and their related habitat.

C5 Gambia licence

Just emailed I get The Gambia licence tomorrow :-)

I'll post a copy here.

This means I will be QRV from C5 22nd - 29th August.

I have someone in Gambia who has paid the GRA for me but the payment has to be made in person. Although PURA did also after I arranged for the local payment, give me the details where you could make payment via a bank transfer into a UK account.

Note the statement that the installation site can be visited without prior notice. I had to give them a lot of details about where I would be operating.

FT817 - Q1104 / 2SJ355 P-FET

This is the rear of the main board.

The Q1104 (I think) 2SJ355 P-FET has also blown, the source pin has completely blown out.

Close up with PFET circled.

The DC choke in the top side I have rewound. No photo.

île de Gorée IOTA AF-045

I will activate IOTA île de Gorée AF-045 one day during 15th - 22nd August.


M1KTA/6W will be SSB ONLY!

FT817 more investigation

More investigation.

There are two diodes (on my schematic) between the positive power pin and
the battery pack. It seems some newer units have an internal fuse, mine doesn't. Obviously either or both of the diodes (and/or the fuse) could have gone open circuit. I do not run my FT817 with batteries anyway. According to the circuit D1084, if it fails, would prevent operation on internal power (assuming no other damage). D1085, if it fails will prevent operation (and charging) on external power.

I will need to check the board which means some disassembly... the printed circuit traces (the techlab at work recommended checking them after I mentioned the problem) may also have melted.

The rather obvious failure I have seen of the T1035, a bifilar wound choke, the purpose of which is to isolate the external +ve from ground, is affected. Reading lots of group posts and it seems that some of the very early units (mine is August 2005) experienced catastrophic melt- down when insulation on this choke melted, allowing positive and negative supply leads to short together more or less permanently.

Sounds a bit like mine maybe?

My serial is 5G990117. Asked how can I work this out. The serial number has the form YMLLNNN where Y = the last digit of the year of manufacture, M is a letter representing the month of manufacture with "C" = January, "D" = February, and so on, the lot number is representated by the two digit LL (00 - 99), and NNNN (0001-9999) is the unit number within lot LL.

The only other thing I can find out from http://www.ka7oei.com/ft817_calibrate.html is that the voltage drop across T1035 is used.

18
HF1-IC
This sets the maximum amount of current that the radio can draw when transmitting in the HF1 band (0.1-<2 .5=".5" across="across" and="and" by="by" current.="current." drop="drop" finals="finals" font="font" for="for" higher="higher" is="is" measured="measured" mhz.="mhz." monitoring="monitoring" nbsp="nbsp" of="of" one="one" overcurrent="overcurrent" protection="protection" radio="radio" s="s" t1035.="t1035." the="the" this="this" values="higher" voltage="voltage" windings="windings">

I guess the danger is that the 13.8V line is connected to the PA/Finals. J1015 on the main board diagram.

And in through J3003 on the final diagram.

That the choke melted was it because the finals had failed or due to something else. The main board ribbon connector J8008 and associated 13.8V tracks show no damage.

The radio was in RX mode only at the time so hoping it was not the finals.

Now to find time and do the disassemble.

I will have Clive M5CHH FT817 side by side for comparison as I run through this.