Yaesu ft225rd manual

Not all appliances and electronics have Tech Sheets or Fast Track publications. Training Manuals generally contain more in-depth servicing information and circuit explanations. This series of articles is inspired by the large scale test of two meter transceivers that was published in RT no 3.

Besides excessive sideband noise we found that some stations create severe keying clicks - a phenomenon that many two meter operators have obvious experiences of. We also found that the bandwidth of the ssb transmit signal was too large, although not disastrously.

After having treated the sideband noise in four transceiver types it could be appropriate to treat keying clicks and ssb splatter. In the large scale test FTRD was the worst rig in ssb mode causing quite a lot of splatter. It also has severe keying clicks, so this station is a good candidate to demonstrate how to proceed. It is easy to remove keying clicks completely.

It is quite simple to make the keying perfect in FTRD. In the keying circuitry there is a pulse shaper, Q It is followed by a low pass filter R and C C is loaded by R which goes to the base of the keying transistor Q By replacing C, a 0. The fall time is about 2 milliseconds at the antenna connector. The rise time is shorter. In one of the rigs we adjusted it by connecting a 27 kiloohm in parallel with C In the other station R was only 10 kiloohm the schematics show 47 kiloohms.

For perfect keying one more modification is required: The signal from the collector of the keying transistor is keying the transmitter in two ways. Firstly it goes to the emitters of two of the transmit amplifier stages.

Secondly it goes to the source of Q, a power regulating transistor. The voltage swing required to control Q is much smaller than what is needed to control the emitters. A voltage divider is required to reduce the amplitude of the keying signal at the source of Q Without this voltage divider one gets dual time constants in the output signal. By use of three resistors one gets perfect keying. The resistors are placed on the connector J22 mic amp unit PCB connector.

See the photo, fig 4. Note that the numbering on the connector does not agree with the numbering in the circuit diagram! Here is a step by step description: Remove the wire that connects B3 to B6. B3 on the PCB connector is numbered 6 in the circuit diagram and B6 is numbered A3 is numbered 5 in the circuit diagram.

With the modifications described above the keying speed is limited. The rise and fall times of 2 milliseconds should allow around letters per minute, but the time delay in the keying circuitry is large and makes the maximum speed much lower.

We will come back to that in a later article. Fig 3. A resistor may be connected in parallel to C on the other side of the board. That resistor and R determine the rise time, see the text. The fall time is determined by C and R Peak power versus average power in ssb The simple and cheap modifications we have described sofar in this series of articles are uncontroversial and we hope the manufacturers will incorporate these in their future production!

For the FT RD only one wire has to be moved in order to eliminate completely the splatter in ssb mode. This way of curing ssb splatter is however not entirely uncontroversial but it is of fundamental interest.

For that reason here is first a short general discussion about ssb. When designing a ssb transmitter for amateur use two entirely different starting points are possible: 1. No substitutions! Next Pull one board at a time.

Good luck. N7DFF , Apr 26, This sometimes burns out. This adjusts the maximum carrier level on FM, and is accessible from the top of the rig after removing the plastic cover over the audio board.

I've never actually found this in the manual, but I expect it's there somewhere. The audio output transistors are prone to failure, but it should be noted that they can often destroy the audio driver and some of the associated resistors.

Let us know what you traded it for and help other ham operators! Price History Chart. Login or Register to submit prices. If you have any questions or suggestions, or if you'd like to participate, please get in touch. Rig Reference Ham Radio Equipment. Specs Manuals 0 Reviews 0 Prices 3 Compare.