Monday, April 28, 2008

Yaesu FT-221 144MHz Transceiver.

Installed at the QTH is an old but reliable Yaesu FT-221 fitted with a Mutek Front End Board for monitoring of SSB on the lower portion of the 144MHz band for possible long distance contacts with BV. This was quite a common occurrence at my last QTH during the last cycle and a good number of BV contact were made.

About the Mutek Front End Board:

RPCB 144ub Replacement board for the Yaesu FT221 and FT225 Transceivers -

Mutek Limited produces a series of high performance RF/IF replacement boards for the FT736, IC251, IC271, TS700S, FT221, and FT225 that will turn any of these radio's into competition grade high performance receive systems. These boards are a redesign and replacement of the radios RF preamplifier, lossy PIN diode antenna changeover switches, bandpass filters, mixer, and IF amplifier section including in most cases the crystal filter. Low loss antenna relays, low noise preamplifiers, three pole filtering plus high dynamic range shottky Double balanced mixers (DBM's) and high quality crystal filters are featured in muTek's replacement boards. The addition of a muTek board will yield a radio with an excellent noise figure and a high dynamic range ----- performance that you could only dream of in the past.

The RPCB 144ub is the replacement board for the Yaesu FT221 and the FT 225 transceivers. It is supplied with complete installation instructions as well as interconnecting cables. The board replaces the original board in the transceiver and is the simplest of the front end kits to install. This board features a low noise front end, Tchebyshev bandpass filters, diode ring Double Balanced Mixer (DBM), IF amplifier plus an 6 pole 15KHz crystal filter. No alignment is necessary after installation of the board.

Technical description of Yaesu FT-221:

Frequency Range 144.0 MHz ~ 148.0 MHz

Emission: AM FM SSB (LSB and USB) and CW

Power Output:
SSB 12 Watts PEP
FM, CW 14 Watts
AM 2.5 Watts

Principle: Superhet with RF-stage; IF-Freq. 10700 kHzSuperhet with a preamplification stage. Permanent Magnet Dynamic (PDyn) Loudspeaker (moving coil)Permanent magnet type moving coil speaker (principle by Rice-Kellog, without field excitation coil).

General: Dimensions (WHD) 280 x 125 x 295 mm / 11 x 4.9 x 11.6 inch

In FM-mode double-conversion, second IF 455 KHz. Later "R"-version have modified frequency-offset-control for FM-repeater operation and few minor changes on back-panel. In Europe also sold under Sommerkamp label.

The frequency is set by a 500KHz VFO being mixed with the product of a number of crystals and is displayed using a rotary display dial.

The top of the case is removed by opening 4 quick release fasteners, revealing a number of user adjustable trimmers and pots. The modular design of the FT-221, where removable circuit boards allowed radio hams to modify their FT-221 either by replacing specific components or even replacing the whole board [Mutek]. One such replacement is the mutek replacement front end board which improved the front-end sensitivity. The open format of the internal construction also allowed the transmit and receive cables to be brought outside the case to use a low-noise coaxial relay.

Below is a photo of the 5 element Diamond yagi antenna installed and point roughly 5o deg. The black coating is high temperature black paint sprayed on to prevent aluminium corrosion:

Below is the Mutek direct plug in replacement Front End Board for the FT-221 transceiver:

No comments: