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Background on the RX-321:
Correspondence between GW & Ten-Tec shows that development of the RX-321 started in 1999. This seems to coincide with the beginning of GMDSS useage:
"The Global Maritime Distress and Safety System (GMDSS) is an international system which uses improved terrestrial and satellite technology and ship-board radio systems. It ensures rapid alerting of shore-based rescue and communications authorities in the event of an emergency. In addition, the system alerts vessels in the immediate vicinity and provides improved means of locating survivors."
"GMDSS was developed through the International Maritime Organization (IMO) and represents a significant change in the way maritime safety communications are conducted. While it is mandatory for all ships subject to the International Convention for the Safety Of Life At Sea (SOLAS) (cargo ships 300 gross tons or greater and all passenger vessels, on international voyages), GMDSS will impact on all radio-equipped vessels, regardless of size. The global implementation of GMDSS services became effective on February 1, 1999."
"Ships fitted with GMDSS equipment are safer at sea - and more likely to receive assistance in the event of a distress - because the GMDSS provides for automatic distress alerting and locating when ship's staff do not have time to send out a full distress call. The GMDSS also requires ships to receive broadcasts of maritime safety information which could prevent a distress from happening, and requires ships to carry satellite Emergency Position Indicating Radio Beacons (EPIRBs), which float free from a sinking ship and alert rescue authorities with the ship's identity and location."
GW put these up for auction as surplus equipment on Septemtber 17, 2002. A scan of this original offering is on the photo page.
The first public notice of the RX-321 I could find was from September 2003:
RX-320 users:
If you were wondering if Ten Tec was ever going to issue a model RX-321, be curious no longer. Globe Wireless contracted with TT a couple of years ago to produce a modified version of the RX-320 for shipboard use as a secondary receiver in our shipboard communications system, and Ten-Tec designated it the RX-321. GW was able to do this as GW is one of Ten-Tec's single largest customers. GW uses the RX-330(A&B) and the RX-331 receivers at their shore side stations of their global HF digital maritime communications network. They have well over 300 of them in use worldwide with great success.
TT will not be releasing the model RX-321 for sale to the general public.
Essentially, it's a repackaged RX-320 in a slightly larger, better ventilated cabinet, using a barrier strip for speaker audio output and DC power input (12-28VDC), a DB9-M for low-level audio and "remote" features, and an SO-239 for RF input. Internal modifications include slightly different firmware and a higher-stability reference oscillator.
Internally, the RF/audio PCB is different, larger than the RX-320, hence the need for a larger case. There is also an added voltage regulator subassembly affixed to the top of the cabinet to deal with the higher allowed power supply voltage.
The RX-321 utilizes the same serial control interface as the '320. TT control software (and others, including the Palm OS version) works exactly the same. Receiver parameters available (as observed) are the same.
There is a difference in receiver performance that is immediately obvious when compared to the 320.
When changing synthesizer frequency, there is significant "chuffing" (short noise bursts as the synthesizer steps in frequency) at times, enough to make VFO type operation (many steps over a short time interval) somewhat annoying to the listener.
The RX-321 is intended for use in a channelized system without the need for frequent retuning. The "chuffing" is probably a result of lengthened PLL loop filter time constants to improve the phase noise characteristics of the synthesizer, and the chuffing noise is generated as the PLL unlocks temporarly upon a frequency change.
There is a compromise in PLL design between lock time and VCO phase noise, and apparently TT chose to favor decreased phase noise over lock time in their design, which is acceptable in this application. This keep costs down by eliminating the need for a higher-performance, i.e. more complex and expensive synthesizer.
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Details:
The RX-321 was based on the RX320 and was built to their specifications for Globe Wireless for a shipboard GMDSS project.. Globe Wireless abandoned the project and sold off the unused units - best guess as to quantity is around 100 units.
The RX-321 is slightly larger and more robust than the RX320 to accommodate a larger RF front end board that is different than the RX320 RF front end. It includes a removable mounting bracket to facilitate mounting on a bulkhead or table.
The intermod specs are improved. The RX320 is spec'd at 3rd order at +10 dBm while the RX-321 is spec'd at +15 dBm. The second order intercept of the RX-321 is spec'd at +60 dBM while the RX320 is not specified.
The two oscillator cans on the RF board are not "ovenized" but are TCXOs (Temperature Compensated Crystal Oscillators) built most likely by Fordahl and are spec'd at +/- 10 Hz over 0 to 40 degrees C. These TCXOs bear the part number of "DFA 14 KHV".
From Fordahl's "Generic Ordering Codes" sheet this part number translates as:
DFA = TCXO
14= DIL 14 (dual in-line 14 pin)
K= -30 to +60 degrees C
H= HCMOS logic level output
V=external control voltage.
That final V suggests the little pots (R104 and R106) next to the oscillators create a trimming voltage to put each on its frequency.
RF board: 7 front end filters added. switched by pin diodes. Doubly balanced (4 JFETS) first mixer
Extra serial data chip to provide filter choice voltages. Different 1st mixer, looks like double-balanced quad fet mixer for higher IP values. AGC injection on 3 points, extra gain controlled dualgate fet right after 45 MHz IF filter. Pindiode AGC after preselection/after 45Mhz filter. Firmware diff: don't know but extra serial data for frontend filtering.
The active antenna circuitry inside the RX320 is gone with the RX-321. That circuit could have been a source of intermods.
The antenna connector is an SO-239 on the RX-321 instead of the RCA plug on the RX320.
The DC power is shown as 12-28VDC on the RX-321 instead of the unspecified power on the RX320. Power supply: seperate board for voltages. Also a step-up voltage regulator for higher voltages for frontend ? I measured 18V to front end. Low ripple and noise.
DC power and the speaker connect via a terminal strip on the RX-321 while the RX320 uses phone plugs and DC coaxial connectors. TCXO's for 2nd and 3rd LO oscillators.The RX-321 is dead on within 10Hz cold or warm.
RS232 device is a ADM232AARN instead of max232 type.
Remote audio line out on the RX-321 is a balanced, center tapped transformer. Linelevel audio output through seperation transformer, balanced audio out.
The RX-321 has a mute connection.
The RX-321 comes with a nice little 120 VAC to 12 VDC switching power supply.
The RX-321 has a power LED and a more rugged power switch.
The RX-321 runs on RX320 software and it seems to work just fine with all functions doing what they should. The DSP board is slightly different with a different part number and different EPROM identifier.
The IF is not brought out like on the RX320D for digital radio. The cable can be spliced and an IF output added.
It works down to 100 kHz. Apparently it does not require a mod like the RX320 does to perform well at lower frequencies.
Temperature: with an ambient temp of 65F, the case interior runs at 80F whether on a fixed frequency or scanning.
Case dimensions: 7-9/16"D x 7-13/16"W x 2-15/16"D. PSU: 4-5/8" x 3-7/8" x 1-1/4".
Reported specs on the original RX-320 are:
The receiver’s IF bandwidths are 8, 5, 2.5, 1.8 and 0.5 kHz (shape factor 1.5:1 or better)
AM sensitivity is rated as 0.64 uV with the wide filter (80% modulation, one kHz tone, 12 dB S+N/N).
SSB sensitivity is 0.3 uV with the 2.5 kHz filter.
Third order intercept is specified as +10 dBm with a 90 dB dynamic range with the 2.5 kHz filter with 50 kHz signal spacing.
The radio is a triple conversion design with intermediate frequencies of 45 MHz, 455 kHz and 12 kHz-the final conversion being for the DSP circuitry.
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RX-320 vs. RX-321:
The RX-321 has the following physical differences from the RX320:
1. There is NO Line Out.
2. There is NO whip antenna.
3. An external antenna is required, via the UHF connector.
The RX-321 has the following Performance Improvements:
1. TXCO oscillators w/ +-10 Hz frequency stability. (0 to 40 C) versus +/- 100 Hz at 25° C on the RX320.
2. 2nd order intercept +60 dBm.
3. 3rd order intercept +15 dBm, versus +10dbm on the RX320
4. Seven front end filters.
RX-321 REMOTE (Db9-M) connector pinouts (as reverse engineered from pcb...)
Pin 1 Line audio (balanced)
Pin 6 Line audio (center tap)
Pin 2 Line audio (balanced)
Pin 5 Mute (?) (ground to mute?)
Pin 9 Ground
The line transformer is a standard feature of remote
site receivers for 600R balanced lines.
As delivered to the customer there's a hardware remote control, with volume and on/off
controls, two GMDSS modules, as well as a speaker and LED indicators all in a machined box. Also included is a spool of coax cable, and a huge weatherized metal enclosure.
As far as I can find out, no 12KHZ outputs were originally installed but were added by various owners, either wired to a separate jack or to an unused pin (pin 3 or pin 4) on the remote connector.
If you would like to compare these specs to some other Ten-Tec radios, here are reviews of the RX331, RX340 & RX320D
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RX-321 Serial Numbers:
Links go to submitter's Yahoo profile or email. Reformatted at the suggestion of Jason Garcia!
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TEN TEC SERIAL NUMBER DECODING - from the archives at lists.contesting.com. Also found on the Ten-Tec Wiki.
Example: Serial Number 06A10108
06 at the front is month of manufacture, or scheduled production run month. If we were scheduled to build a run of a particular model in June, and for some reason we were delayed to July or August for that particular run, we'd still put "06" at the front of the serial number. "A" is a separator between the groups of digits. "1" is the production run # for that particular month. "010" is the unit number. "8" is the year of manufacture.
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