[amsat-bb] Re: Wish List, The Ideal VHF/UHF Sat Rig

francesco messineo francesco.messineo at gmail.com
Mon Mar 1 12:30:50 PST 2010


beeing an engineer (RF/telecom) and V/UHF (and sat) addicted, I'm
always thinkin about this very same issue, but I think that the best
RTX would come from a bunch of engineers with an "open source" like
project, not from one of the current manufacturers. Why? First because
 one such rig would cost too much in engineering research and project
(if it really need to be state of the art and no compromise); secondly
because no one would buy the next rig if such a great RTX would really
As for the features, comments are in line

On 3/1/10, MM <ka1rrw at yahoo.com> wrote:
> 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).

Ok for USB, maybe ethernet, but I'd put the controlling software on
the PC/computer end, CPU in my opinion needs to do only the essential
non the inside of the RTX, we don't really need heavy digital
noise/birdies and no necessary power consumption. You need to have a
computer anyway. Yes, digital noise and birdies can be confined, but
if it's the least possible from start, I'd vote for it.

>  •       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.

it's good to have power level set by software settings in case of
amplifier presence. However many solid state amplifiers have poor IMD
performance when operated at a lower setting. This needs to be
addressed from the project stage.

>  •       TX/RX Sequencer built-in, to control external Preamps, Amplifies and other accessories (programmable).


>  Receiver:
>  Of course we need a "Great" receiver, not another mediocre receiver.
>  Each receiver for each band needs to be a "Great" performer.

separate receivers and transmitter chains, in my dreams the RTX can
host one module per band and one module per IF, yes, two separate IF
chains are a must for satellite work or just to monitor two bands at
time. One could also chose analog or fully digital IF module too.
Let's say 4 bays for band modules and two bays for IF modules.
Of course all IF stages are accessible both pre-filtered and post-filtered.

>  No Birdies:
>  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.

I'd add, the lowest possible phase noise on conversion oscillators,
I'd have no more than two total conversions per band. All oscillators
locked to internal or external 10 MHz reference.

>  Filters:
>  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)
>  Example:
>  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.
>  Other Modes:
>  CW, FM-2.5k, Data

that can be straightforward on digital IF, for analog IF I'd stick
with 3 per mode and optional, not everyone will need every mode.
What AM is for anyway?

>  Audio Quality:
>  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.

I'd drop this. I'd rather have very low distortion audio amplifiers
with maybe a large enough BW to let the FM guys have their chat on
repeaters, even if I prefer to think about an high performance rig,
not a very general purpose rig. Audio BW shouldn't be more large than
what's needed to match the widest IF filter anyway. We don't want any
noise added for weak signal operations.

>  VHF / UHF Bands built-in, with competition grade TX/RX:
>  6-meters        50-54

make it 40-60 MHz on RX, lots of opening indicators to watch for.

4-meters is also a must
60-80 MHz RX, tx can be 69.5-70.5 MHz.

>  2-meters        144-148
>  70-cm           420 - 450

I wouldn't make it that large, we need good RX performance and tuned
frontends are a must.
Probably 430-450 can be still made good, but I wouldn't do more and
anyway leave a 430-440 MHz module as an option for region 1.

>  23-cm           1280 - 1300
>  (All frequencies localized for each country)
>  Transmitter outputs:
>  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.

think about satellite only, 100W out is ok for sat only. I'd stay with
the classic 100W per band and have clean low power menu-settable
options for linears owners.

>  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.

they will hardly agree. It's better to have a versatile transceiver
that can interface with everything the engineers can think of.

>  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

I'd stick with 100W from 6m to 70cm, the others at 10W can be ok.

>  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.

one minute at 100% power, nothing less. Some countries have > 1Kw
legal limit, it's possible that such amplifiers require 100W drive
levels. Also, meteorscatter operation on lower bands is common with
the 100W level, so why upsetting the happy QRPers?

>  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.

I'd leave it as an option maybe. Nice to have, but makes the thing
bigger and power hungrier.
On VHF we usually are happy with a fast memory scan on beacons and
maybe TV carriers.

>  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.

that's good, but leave the effort to PC programs.

>  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.

I always find mode B easier to work with manual doppler corrections.
The higher band is the TX band, so usually I only have to turn one
knob during a QSO even if the other party is using only higher band
manual correction like I'm doing.

>  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.

if modular, each of the IF strips will have its completely independent
VFO, both can be linked for satellite operations anyway.

>  DSP Noise tools:
>  The usual stuff.

well, yes, but please tunable notch. And I mean TUNABLE.

>  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.

true, doppler impact is reduced on FM, typically also the QSO
possibility are reduced because the one channel is a mess (at least
over europe).

>  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.

yes, FM discriminator is good to have, I'd add AFC to automaticly tune
to the center of the FM channel.

>  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):

not easy (or cheap) to have good receivers if too large.
In my modular dream each module has different RX frontend filters for
each sub-band (like each 5 MHz on 6m or even less).

>  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.

that could be a separate module to add for the police listeners :)

>  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

if the dream rig is made modular from the beginning, this will never
be a problem again.

>  (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 HF:
>  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.

not true, you could easily add an HF module and that would not degrade
the performance of everything else (on satellite we still have a 29
MHz sat!), the secret is "modular".

>  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.

not true if everything is modular. The terrestrial or EME guys could
start with two modules (6m/2m maybe) and one single IF module, either
the digital one or analog one. The sat-only guy would only need
2m/70cm module and the two IFs. One day he would add the HF module to
work AO-07 mode A.

>  No obsolete Serial ports:
>   No RS-232 or TTL.
>  These devices are so last century.

they still work very well however. I wouldn't miss it, but always
think about the engineer point of view: both USB and ethernet require
higher clock rates and produce more digital noise to filter out.

>  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.

agreed, I don't see how DSTAR can find a place in the DX V/UHF world.

>  How much are we willing to pay for the HR-956-Pro:
>  That depends on the performance, suggest price $2000 - $3000 USD

it depends.... state of the art electronic isn't necessarily
expensive. Look at low phase noise oscillators/buffer/amplifiers and
high performance frontends, they're not that much costly than  poor
performers. All digital IFs are a reality and we could even think
about direct digital frontends at least on the lower VHF bands. It's
engineers that know how to do them right that cost. An "open source"
kind of approach might work, if we hope a big manufacturer is going to
make a dream trasceiver, I'm afraid I'm not going to buy a newer
transceiver soon.

It can be done, I'm definitely sure.

Frank IZ8DWF

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