[amsat-bb] Wish List, The Ideal VHF/UHF Sat Rig
ka1rrw at yahoo.com
Mon Mar 1 10:44:00 PST 2010
My Ideal Competition Grade VHF/UHF Radio Wish list.
It seems we are long over do for a Competition grade high performance VHF/UHF transceiver, which can also be used for Satellite operations. There are several competition grade HF transceivers on the market, however there are no high end competition grade VHF/UHF/Satellite systems on the marker.
Most of the rigs I have seen which support VHF/UHF are either HF rigs that have had VHF/UHF slapped on, or low end VHF/UHF rigs, with HF slapped on.
If we want the Amateur Radio manufactures to build us a "GREAT" VHF/UHF/Satellite system, then we need to tell them what we need.
Here are some suggestions. Constructive comments welcome.
This radio does not exist.
If the manufactures are interested in providing a new state of the art VHF/UHF radio to the Amateur Radio community, here is one opinion of what should be in next Competition Grade VHF/UHF Transceiver and what should not be in the radio.
I am going to give this fictional radio a name HR-956-Pro.
What do we need:
• We need a competition grade VHF/UHF transceiver that will support Terrestrial-DX, Satellite and EME operations (Voice, CW and Digital-JT65).
• The HR-956-Pro, needs to be able to interface with modern computers (HTML Browser, USB and or CAT-5).
• The HR-956-Pro, needs to able to interface with modern Externally mounted Pre-amplifier (both power feeds and transmitter sequencing).
• The HR-956-Pro, need to be able to interface with modern Solid State Amplifiers and Tube based amplifiers. The RF output per band needs to be standardized with the Amplifier manufactures to prevent transceiver and amplifier failures due to sequencing problems and RF mismatching.
• TX/RX Sequencer built-in, to control external Preamps, Amplifies and other accessories (programmable).
Of course we need a "Great" receiver, not another mediocre receiver.
Each receiver for each band needs to be a "Great" performer.
On a HF rig, a few Birdies do not usually cause serious issues, since the HF users are often listening to signals "Above" the noise floor. On a Satellite Radio, we are often listening to signals 10-30 dB, "Below" the Noise floor. Internally generated birdies are a serious problem for weak signal VHF/UHF operations.
Each mode will need its own selection of DSP filters. The filters would also affect one of the Line-level outputs to the external PC. There are times when want to send Filtered or unfiltered audio to your external PC for Digital signal processing. One of the line-level outputs should be taped before the HR-956-Pro Filters, the other line-level output should be taped after the HR-956-Pro filters. The TX and RX filters should be independently selectable.
The Filters need to be tested to verify they will support Satellite Mode-J (TX on 2-meters while listening on 435-438)
FM-5k, Filters 15k, 10k and 8k filters.
AM Filters 10k, 6k, 3k, etc.
SSB Filters 4.0k, 3.0k, 2.5k, 2.0k, etc.
CW, FM-2.5k, Data
Life is too short for QRP or Poor Audio.
It's not the number of contacts that’s important, it’s the quality of the contact.
On the audio side, the HR-956-Pro needs to be able to support a wider range of audio through most of the stages. Of course the radio needs to meet FCC and other requirements, however we can still design the radio to deliver a wider bandwidth of good sounding audio.
Let's shoot for 100-4000 Hz, on both TX and RX audio circuits. This will also mean, that a better stock microphone design will be required.
VHF / UHF Bands built-in, with competition grade TX/RX:
70-cm 420 - 450
23-cm 1280 - 1300
(All frequencies localized for each country)
A high power transceiver is less desirable than a low power transceiver.
Let me explain:
For serious Terrestrial DX and EME you need to run more than 100 watts. A VHF/UHF transceiver designed for high power ( 100 watt range) transmitting, would not be compatible with third-party amplifiers or pre-amplifiers.
Most VHF/UHF amps are designed for 25 or 50 watts maximum input.
The manufactures of Transceivers and Amplifies need to agree upon a set of standard power level so the third-party amplifier manufactures can design properly matched Amplifiers and pre-amplifiers. This will also help reduce the number of transceiver and amplifier failures caused by mismatched RF settings.
Suggested standards for VHF/UHF bases stations:
6 Meters 50 watts
2 Meters 25 watts
70 cm 25 watts
900 mc 10 watts
1.2 gig 10 watts
The duty cycle of the competition grade system, will also need to be greater than a 70% duty cycle.
A typical EME link running JT65 requires a 50% for 10-30 minutes at a time. The transistors and cooling system needs to be designed accordingly to meet the competition grade requirements.
HR-956-Pro Must have list:
Spectrum display screen:
I can't imagine building a new competition grade system without this feature.
It would be nice to see the band pass, before and after the filter stages.
Full computer remote control:
Memory read/Read and save. All memory channels options must be exportable to a CSV or similar file, including TX and RX frequencies, settings, including Repeater or split frequency settings.
All protocols must be Public protocols, no propriety software or licenses.
Doppler Control (Manual):
LEO SSB satellites are some of the hardest satellites two work because of the amount of Doppler frequency change per second. Satellite Mode-B is very hard (70 cm Uplink and 2-meter Downlink). While you are talking through a SSB Mod-B satellite, you need to be simultaneously adjusting your transmitter with every other word, in order to keep your downlink signal centered inside the transponder.
The Yasue FT-736R Satellite control knob, seems to work very well with dual VFO's and provides you the ability to quickly change either TX or RX to compensate for Doppler (among other features). The Knob style is much easier to use than "Buttons". I found the Doppler VFO correction on some newer radios to be very frustrating.
The new HR-956-Pro must have the Yasue FT-736R control Knob and it must be functional for both VFO's and Memory Channels.
DSP Noise tools:
The usual stuff.
FM Center Tuning Meter:
Many of the new satellites are LEO's (Low Earth Orbit), and many of these satellites are running FM-5k. The reason for FM is because the Doppler causes the 70cm band to drift over 20, kHz during a 10-20 minute pass. The LEO SSB satellites using Mode J or Mode B are difficult to use because of the large Doppler change. The FM mode, helps reduce the impact caused by the higher Doppler.
The FM Center Tuning Meter feature is a "must have" for a Satellite radio.
When the FM satellite comes in range, just look at the FM meter and tune the receiver until the needle is centered and you now know the exact downlink for that Satellite. If the needle is left, turn the RX knob slowly Right, If the needle is Right, turn the RX knob slowly left, very simple.
The Yaesu FT-736R has a FM Center Tuning Meter and it makes working FM satellites much easier. The IC-910 has a blinking light to tell you your FM satellite receiver frequency has drifted. Unfortunately, the blinking light is useless in telling you if your frequency is high or low.
HR-956-Pro, Nice to have list:
General coverage receiver (50 - 1000 megacycles):
The addition of a general coverage receiver would help with the sales of the HR-956-Pro. However, it is very important that the general coverage receiver, NOT degrade the performance of the satellite receivers. We are not trying to build a super police scanner. One possible suggestion would-be to make the general coverage receiver a separate circuit board, which would be connected to a separate antenna port and thus would not degraded from the performance of the satellite receivers.
VHF / UHF Optional bands or Transverter:
The Amateur radio community is constantly experimenting with new bands. It would be nice to have a Transverter module or expansion module for future bands. In the USA these bands are becoming popular, 220mc, 900 mc, etc
(All frequencies localized for each country)
Size is important:
To hold the hardware, band scope, filters and make the buttons easily accessible, a box about the size of the IC-756 product seems to be the right size.
What should not be in the HR-956-Pro.
No access to frequencies below 50 megacycles.
The addition of HF to a satellite radio would only degrade the performance of the weak signal satellite receivers.
HF would also add to the cost of the transceiver and reduce its sales potential.
A competition grade VHF/UHF transceiver has no use for HF.
HF would result in the radio being just another mediocre transceiver.
No obsolete Serial ports:
No RS-232 or TTL.
These devices are so last century.
The DSTAR mode is fun, I use it often and I have even been pushing ARISS to install it on the International Space Station. As much as I like this mode, it is not a requirement for a competition grade satellite system. I would much rather have the money put into making the VHF/UHF receivers the best possible.
How much are we willing to pay for the HR-956-Pro:
That depends on the performance, suggest price $2000 - $3000 USD
If anyone knows of such a radio I would be interested to know who makes it.
More information about the AMSAT-BB