N8YX
10-20-2012, 07:26 PM
Model railroaders have a term for homebrewed rolling stock which uses pieces and parts from various kits: 'Kitbashing'.
We amateurs have similar vernacular for radio and peripheral constructs: Frankenrigs (among other metaphors).
Herein we discuss equipment you've morphed into something else - either from necessity or simply as a challenge.
Back in the day, I built a random-wire tuner from a surplus ARC-5 transmitter. I also learned about RF burns courtesy of that sucker. :lol:
And then came the numerous CB-to-10M conversions. A pair of boots for my HW-8 built from an old Kemtron CB amplifier. An R-820 which is now a dedicated SWBC rig; too bad many shortwave broadcasters are leaving the air.
Latest effort is not driven by the fact that I need another ham-bands only receiver...far from it. Rather, in the Junque Box lies a pile of FT-301/901 stuff and I know there's something unique hiding within.
Somewhat serendipitous is the fact that both of the radios use plug-in cards for their function modules: VOX/Cal, IF, Filter, AF, BFO or AM/FSK. They're also close enough in mixer/IF schemes that one can be converted to the other.
Thus, a FrankenRX project was born. I got hold of a functional FT-301 (analog), a cosmetically challenged FT-301 which won't transmit, a (supposedly good) FT-301D (digital readout), another FT-301 of unknown lineage...and I won another non-operational -D model on eBay Friday afternoon.
eBay also provided another FT-901 Filter Board and an XTAL Board - these parts are essential to part of the project and I need to find one more '901 Filter Board, an IF Board, a BFO Board and an AF board.
Here's what we're gonna do with all of this:
The analog transceiver is going to get a complete HET/Premix crystal swap for the '901 parts, its Filter Board modified for use with the '901-style filters and the BFO/Reject crystals swapped for their '901 equivalents. Additionally, the NB/Proc filter will be swapped for a '901 unit. The "29.0" position becomes 27.0MHz (RX only), the "29.5" slot will cover 24.5MHz , the "Aux" position gets 18.0MHz and the WWV spot becomes 10MHz...VFO tunable, and transceive enabled.
On to the receiver project:
We summarily chuck the VOX/Cal board as it's no longer needed. This opens up a spot for another filter board; both will be converted to use the '901's IF scheme. Fitted on one will be 6/2.4/2.1KHz B/W filters and on another will be 1.8KHz/500Hz/250Hz units. The mode switch will be removed from the filter switching circuit and the spot where the "VFO Select" switch currently resides will have a 6-position switch fitted, thus allowing filter selection independent of mode.
A few sets of those OEM concentric controls will come in handy: The Reject control now becomes an IF Width/Reject control; the now unneeded "Proc" switch serves to turn the Reject (notch) filter on and off in the same manner as this function is implemented on the '901's IF board...which will also be swapped for the '301 part. Similarly, the '301 AF board goes away and the '901 replacement sports an Audio Peak Filter. The "Clar" switch (DPDT/center-off) is converted to a control which functions the same as its '901 counterpart: Center is off, down is Cal(ibrator) and up is APF On.
The outer control of the '301 Clar/Drive combo becomes a squelch or an IF Gain control, the unneeded VOX Gain control is changed to a dual pot and its inner controls the APF frequency while the outer sets the noise blanker threshold.
A new front panel with silk screened, updated labeling is in the works.
In the rear of the rig, the 10w and 100w PA units are to be removed - and if I have enough room to fit it, I'll install a spare '901 FM board in the leftover space. A 6-position Mode switch will be needed...details, details.
The digital readout receiver "FR-301D" will have all of its replacement '901 boards converted over to the standard 9MHz IF scheme of the '301 so as to allow the readout to accurately track the tuned frequency. This requires an order of about half a dozen crystals from ICM in addition to the WARC-specific rocks that will be added to the radios.
HET oscillator injection from transceiver to receiver will ensure the rigs will track properly in transceive mode and will be front-panel selectable from the receiver - similar to Kenwood's implementation of the feature on their R-820.
The project will involve a lot of work and require more parts scrounging. When both receivers are done I'm going to convert their RF Boards to a high-level mixer scheme. Yaesu loved the 3SK40 in an active front end design back in the day. Of course, this only works well when no one else is using the band!
We amateurs have similar vernacular for radio and peripheral constructs: Frankenrigs (among other metaphors).
Herein we discuss equipment you've morphed into something else - either from necessity or simply as a challenge.
Back in the day, I built a random-wire tuner from a surplus ARC-5 transmitter. I also learned about RF burns courtesy of that sucker. :lol:
And then came the numerous CB-to-10M conversions. A pair of boots for my HW-8 built from an old Kemtron CB amplifier. An R-820 which is now a dedicated SWBC rig; too bad many shortwave broadcasters are leaving the air.
Latest effort is not driven by the fact that I need another ham-bands only receiver...far from it. Rather, in the Junque Box lies a pile of FT-301/901 stuff and I know there's something unique hiding within.
Somewhat serendipitous is the fact that both of the radios use plug-in cards for their function modules: VOX/Cal, IF, Filter, AF, BFO or AM/FSK. They're also close enough in mixer/IF schemes that one can be converted to the other.
Thus, a FrankenRX project was born. I got hold of a functional FT-301 (analog), a cosmetically challenged FT-301 which won't transmit, a (supposedly good) FT-301D (digital readout), another FT-301 of unknown lineage...and I won another non-operational -D model on eBay Friday afternoon.
eBay also provided another FT-901 Filter Board and an XTAL Board - these parts are essential to part of the project and I need to find one more '901 Filter Board, an IF Board, a BFO Board and an AF board.
Here's what we're gonna do with all of this:
The analog transceiver is going to get a complete HET/Premix crystal swap for the '901 parts, its Filter Board modified for use with the '901-style filters and the BFO/Reject crystals swapped for their '901 equivalents. Additionally, the NB/Proc filter will be swapped for a '901 unit. The "29.0" position becomes 27.0MHz (RX only), the "29.5" slot will cover 24.5MHz , the "Aux" position gets 18.0MHz and the WWV spot becomes 10MHz...VFO tunable, and transceive enabled.
On to the receiver project:
We summarily chuck the VOX/Cal board as it's no longer needed. This opens up a spot for another filter board; both will be converted to use the '901's IF scheme. Fitted on one will be 6/2.4/2.1KHz B/W filters and on another will be 1.8KHz/500Hz/250Hz units. The mode switch will be removed from the filter switching circuit and the spot where the "VFO Select" switch currently resides will have a 6-position switch fitted, thus allowing filter selection independent of mode.
A few sets of those OEM concentric controls will come in handy: The Reject control now becomes an IF Width/Reject control; the now unneeded "Proc" switch serves to turn the Reject (notch) filter on and off in the same manner as this function is implemented on the '901's IF board...which will also be swapped for the '301 part. Similarly, the '301 AF board goes away and the '901 replacement sports an Audio Peak Filter. The "Clar" switch (DPDT/center-off) is converted to a control which functions the same as its '901 counterpart: Center is off, down is Cal(ibrator) and up is APF On.
The outer control of the '301 Clar/Drive combo becomes a squelch or an IF Gain control, the unneeded VOX Gain control is changed to a dual pot and its inner controls the APF frequency while the outer sets the noise blanker threshold.
A new front panel with silk screened, updated labeling is in the works.
In the rear of the rig, the 10w and 100w PA units are to be removed - and if I have enough room to fit it, I'll install a spare '901 FM board in the leftover space. A 6-position Mode switch will be needed...details, details.
The digital readout receiver "FR-301D" will have all of its replacement '901 boards converted over to the standard 9MHz IF scheme of the '301 so as to allow the readout to accurately track the tuned frequency. This requires an order of about half a dozen crystals from ICM in addition to the WARC-specific rocks that will be added to the radios.
HET oscillator injection from transceiver to receiver will ensure the rigs will track properly in transceive mode and will be front-panel selectable from the receiver - similar to Kenwood's implementation of the feature on their R-820.
The project will involve a lot of work and require more parts scrounging. When both receivers are done I'm going to convert their RF Boards to a high-level mixer scheme. Yaesu loved the 3SK40 in an active front end design back in the day. Of course, this only works well when no one else is using the band!