Product Review!

e have sold quite a few F.M Transmitters to our customers over

the years and in most cases they were happy with the results but invariably

we would receive a call from them wanting to improve two key elements

that being the sensitivity of the microphone and the transmission range?.

Because F.M Bugs have been around for a long time in one form or another

i have found that before you can tackle performance and distance you must have

a reasonable design to start with!.

Recently we decided to do a side by side comparison with the four most commonly

available F.M transmitter kits on the Australian market to see which ones matched up

to there performance claims?.

Without wanting to criticize anyone's products to much!, i can tell you only two of the

models tested lived up to there microphone sensitivity and only the one unit (featured

here) exceded the manufacturers distance claims!.

Performance And Construction!.

The units literature claims a transmission range of at least 1 kilometer when put

together correctly and well quite frankly, im convinced!.

We followed the circuit diagram (its printed on the PCB itself) and kept to the manufactures

instructions and were rewarded with good microphone sensitivity and a total distance of 1.2

Kilometers before units signal faded out!.

The Bug operates on a 9 Volt battery which lasted about 10 days of continuous use which

we found to be excellent, as one of the downsides of high power output transmitters can be

poor battery life!, (of course you don't want the unit to cut out during an interesting conversation!-

you mite miss something!).

Construction Technique And Maximum Range!.

The kit is very easy to construct but on a few occasions our customers have called upon us for

advice with a unit that did not function correctly, apart from good soldering practice we found

a few common mistakes.

Firstly to get maximum range you must cut the provided antenna lead in half to create a

dipole, one piece is soldered into the antenna hole of the PCB and the other length is connected

to the -ve terminal of the battery on the circuit board side, this is mentioned in the instructions

but most people in there haste discard them and just work of the printed board!, this is important

as you wont get the distance unless you make the correct dipole.

Secondly you must make sure the electret mic inserts polarity is correctly soldered into the

board, if its not installed the right way the unit will fail to transmit.

And finally the ZTX-320 main RF output transistor can be a bit sensitive to heat, not overly so

but avoid giving it to much heat, the rest of the parts are bullet proof so theirs no need to be concerned

with them.

Final Notes!.

  Do keep in mind that although this unit is simple to build and a lot of fun to use, some countries

laws may prohibit its use - so check first.

We have actually upgraded the units components and specifications from the standard kit set

to improve its frequency range which currently operates from 85-115 MHz as apposed to the standard

kit sets 88-108mhz.

This was done so that a Scanning Receiver or standard FM Radio could be used to listen to the bug.

 Specifications!.

Battery Supply (9VDC).

Transmission Range (1.2 Kilometers).

Frequency Range (85-115 MHz F.M).

Battery Life- Alkaline (10-12 Days).

 To Purchase This Product!.

P.E.C Order Code. FMK-8750.

Purchase Price. $49.95 AUD (Includes Gst).

Pre- Built Version (Made By Us). $99.00 (Including Gst).

Delivery. $7.70 (Express Post Australia Wide).

O/SEAS AIRMAIL -P.O.A. (Reasonable Rates).