The desired frequency response of a two way radio transmitter is far from flat. It is optimized for maximum intelligibility for human speech, compliance with FCC regulations, and compatibility with any signalling schemes applied to the modulation in the transmitter.
As with magnetic tape and phonograph records the overall signal to noise ratio can be improved by applying pre-emphasis (boosting the high frequencies) in the transmitter (recording equipment) and de-emphasis (cutting the highs) in the receiver (playback equipment). The amount of each is usually agreed on in advance and set by some standards organization.
A voice transmitter will use pre-emphasis, possibly (but not always) some low cut filter to avoid using bandwidth for non speech information like rumble and wind noise and to reduce interference with low frequency signalling, and a high cut filter to avoid creating modulation information that is outside the legal bandwidth for the radio channel being used.
I spent my 41 year career at Motorola designing two way FM radios for the public safety market. Our products were designed to meet the EIA (Electronic Industry Association) standards up until 2011 when the EIA was reorganized into several smaller associations. After 2011, the TIA (Telecommunications Industry Association) standards were used. The TIA standard RS-152B applied to the transmitter, and RS-316B applied to the receiver. These standards were updated as the technology and FCC rules changed. Every year or two the "method of measurement" was updated to reflect the latest $$$ test equipment available from the big players in the test equipment market. The standards were not public domain and rather pricey for a single paper copy.
I never worked on SSB equipment, and Motorola didn't make such equipment for the commercial market, so such standards were not available in our library, and may not apply or even exist on the amateur radio market. Nevertheless the reasons for the non-flatness in the transmitter audio stages are the same, and the occupied bandwidth of a SSB TX signal is about half that of a DSB narrow band FM signal, so similar audio response should be appropriate.
I found a test document online that was obviously for some type of FM radio transmitter similar to what we designed in the 1990's to 2000's era. I included the link.
Notice the 12 db per decade upward slope in the middle. That is the pre-emphasis applied to the transmit audio. The receiver will have a similar response in the reverse direction. This removes about 10 db of hiss in a weak signal FM scenario. An SSB radio channel may not need this much pre / de emphasis due to the lack of FM discriminator noise.
Our radios rolled off everything below 300 Hz at a 12 dB per octave rate to allow for CTCSS and DCS signalling below 150 Hz. This radio does not. Ham HF equipment does not need this rolloff, but transmitted energy in the range below 300 Hz does not improve intelligibility, so it is often eliminated.
There is a sharp drop off above 3000 Hz for compliance with channel bandwidth requirements (often called emission mask) in the public safety spectrum. The flattening of the lower limit above 2500 Hz was added when 12.5 KHz wide channels were authorized. It is needed to meet the emission mask for these channels.
Some rolloff IS needed for FCC compliance in the ham bands, although there are some hams who have different views on interpretation of these specs......and a few hams who operate "HiFi" audio on SSB and use some fancy studio gear to do it. I have heard some of their signals and they do sound like commercial radio broadcasts. Many are down in "5 land."
https://fccid.io/K44475501/Test-Report/RF-Test-Report-2-of-2-2827444.pdf
WZ5Q & VooDoo Audio Crew Hi-Fi eSSB Amateur Radio Stations
I'm starting to look at the transmitter, since I have more or less decided on single conversion with that AD831 mixer chip for at least the first iteration. After using the AD831 for a few weeks, it seems completely satisfactory for this application. I've ordered more of the mixer modules to keep some in inventory, including a few of the ones that use the dual + / - power supply option.
I've also decided to make the transverter modular, so when I change my mind on a whim about something, like adding back up conversion, it won't take a total rebuild to do it. Hopefully.
I want to try to add some leveling, somewhere in the TX chain, either at AF or ALC at RF, so I'm sort of stuck for the moment while I contemplate this.
I'm not sure what to think of the Hi Fi SSB thing.
It seems like modifying those multi conversion DSP transceivers is doing it the harder way than just building a wide bandwidth transmitter from scratch, or using an off the shelf receiver.
The pass band tuners on the old Drake receivers were really good - they can tune continuously from the top of one sideband to the bottom of the opposite. I flipped on the R7 I have here at the office, and it sounds like I put a 6 kHz filter in the 4 kHz position - easy to put the passband at any point of the transmitted audio that you want to listen to on either side of the carrier. These were terrific AM DX machines since you can select any installed filter you want, and just dial in the part of either sideband that is free(est) from QRM or fading, or just sounds best. I have an 8 kHz filter also, but I'm not sure if it is for the R7 or R-4C ; think it is for the 4C line, but can't remember which has which IF off the top of my head ...... I never had an R8, so don't know if they were as good as the R7's.
I had several R7's at one time, but sold or traded all but one off. I still have no rig at home after the lightning debacle, except the FT-817, so I might take the R7 home and try to give a listen for these guys.
Win W5JAG
I've also decided to make the transverter modular, so when I change my mind on a whim about something, like adding back up conversion, it won't take a total rebuild to do it. Hopefully.
I want to try to add some leveling, somewhere in the TX chain, either at AF or ALC at RF, so I'm sort of stuck for the moment while I contemplate this.
I'm not sure what to think of the Hi Fi SSB thing.
It seems like modifying those multi conversion DSP transceivers is doing it the harder way than just building a wide bandwidth transmitter from scratch, or using an off the shelf receiver.
The pass band tuners on the old Drake receivers were really good - they can tune continuously from the top of one sideband to the bottom of the opposite. I flipped on the R7 I have here at the office, and it sounds like I put a 6 kHz filter in the 4 kHz position - easy to put the passband at any point of the transmitted audio that you want to listen to on either side of the carrier. These were terrific AM DX machines since you can select any installed filter you want, and just dial in the part of either sideband that is free(est) from QRM or fading, or just sounds best. I have an 8 kHz filter also, but I'm not sure if it is for the R7 or R-4C ; think it is for the 4C line, but can't remember which has which IF off the top of my head ...... I never had an R8, so don't know if they were as good as the R7's.
I had several R7's at one time, but sold or traded all but one off. I still have no rig at home after the lightning debacle, except the FT-817, so I might take the R7 home and try to give a listen for these guys.
Win W5JAG
I have lived in this house for almost 4 years. I haven't put up an antenna since I din't think that it would work being in a "holler' surrounded by 300 foot ridges on 3 sides. The one on the south side is a good distance away though.
I ordered a couple of those cheap Chinese walkie talkies. Since the FCC has initiated a ban on them, I figured I would get a couple while I still could. I programmed them up on some repeater frequencies in the surrounding towns and was completely surprised to find that I can hit two out of four of them from inside the house, and one of them is UHF (444 MHz) about 6 miles to the south. All I can say is that it must be way up on a hill somewhere.
Maybe it's time to string up a wire and connect up my 817.....if I can find it.
I ordered a couple of those cheap Chinese walkie talkies. Since the FCC has initiated a ban on them, I figured I would get a couple while I still could. I programmed them up on some repeater frequencies in the surrounding towns and was completely surprised to find that I can hit two out of four of them from inside the house, and one of them is UHF (444 MHz) about 6 miles to the south. All I can say is that it must be way up on a hill somewhere.
Maybe it's time to string up a wire and connect up my 817.....if I can find it.
There is a ban on cheap Chinese HT's?
I wonder how successful that will be. They are amazing value for the money, in a non critical application. I rarely use my HT1250 anymore.
I think most of them are based around that RDA1846 SDR chip. I have the datasheet for it, but mine is watermarked "confidential" all over it, so I guess I can't upload it here, but I'm sure it is all over the internet. With the same watermark.
I have some of the DRA817U VHF versions of this module:
UHF Band HAM Radio Module Amateur Radio Walkie Talkie Module DRA818U | eBay
but haven't got around to using it, yet. Figured I would replace the old 80's rockbound 2 meter rig, with a homemade Baofeng. The latest project is taking longer than I anticipated.
Win W5JAG
I wonder how successful that will be. They are amazing value for the money, in a non critical application. I rarely use my HT1250 anymore.
I think most of them are based around that RDA1846 SDR chip. I have the datasheet for it, but mine is watermarked "confidential" all over it, so I guess I can't upload it here, but I'm sure it is all over the internet. With the same watermark.
I have some of the DRA817U VHF versions of this module:
UHF Band HAM Radio Module Amateur Radio Walkie Talkie Module DRA818U | eBay
but haven't got around to using it, yet. Figured I would replace the old 80's rockbound 2 meter rig, with a homemade Baofeng. The latest project is taking longer than I anticipated.
Win W5JAG
FCC Enforcement Advisory states that these can NOT be imported, sold or USED in the USA, even by someone like myself who has a valid ham radio license and would use it only on ham frequencies in a legal manner.
The wording of the FCC document is very unclear and can be interpreted differently by whoever reads it, so parties on both sides of the issue have demanded clarification. Meanwhile the radios are still abundant on Amazon and Ebay, but the prices are rising, especially on Ebay for USA stocked radios. I got a Baofeng BF-F8HP "high power" analog FM radio and a Radioddity GD77 which does analog FM and DMR. There are no DMR repeaters near here byt I might have to DIY one in the future. Meanwhile I programmed them both for 4 local FM ham repeaters.
YouTube
The wording of the FCC document is very unclear and can be interpreted differently by whoever reads it, so parties on both sides of the issue have demanded clarification. Meanwhile the radios are still abundant on Amazon and Ebay, but the prices are rising, especially on Ebay for USA stocked radios. I got a Baofeng BF-F8HP "high power" analog FM radio and a Radioddity GD77 which does analog FM and DMR. There are no DMR repeaters near here byt I might have to DIY one in the future. Meanwhile I programmed them both for 4 local FM ham repeaters.
YouTube
I have some Wouxuns 144/440 and looked at them on my Aeroflex 1200s spectrum analyzer , very clean signal.
Wouxun Electronics Co., Ltd , Professional Two Way Radio Manufacturer
Wouxun Electronics Co., Ltd , Professional Two Way Radio Manufacturer
I haven't connected any test equipment to either radio yet, but when my curiosity gets the better of me AND I have a clean spot on my work bench, I'll probably test, and take apart one or both radios, on camera.
The "clean bench" criteria is the limiting factor right now since there are two half finished projects on it....one is awaiting some table saw time for the wood work, and it is raining again, so.......
The "clean bench" criteria is the limiting factor right now since there are two half finished projects on it....one is awaiting some table saw time for the wood work, and it is raining again, so.......
When Baofengs are outlawed, only outlaws will have Baofengs?
Attached is the order against that importer, and the "Ban".
I still remember all those CB'ers working DX on about any frequency they wanted, and any power level; I'm not sure there was any rule that was not violated with absolute impunity in that fiasco, so it does not set well with me to threaten hams using a 4 or 5 watt radio on our frequencies within the confines of our licenses.
Win W5JAG
Attached is the order against that importer, and the "Ban".
I still remember all those CB'ers working DX on about any frequency they wanted, and any power level; I'm not sure there was any rule that was not violated with absolute impunity in that fiasco, so it does not set well with me to threaten hams using a 4 or 5 watt radio on our frequencies within the confines of our licenses.
Win W5JAG
I read the two actions and they are extremely vague.
How could you know the device can be programmed outside of amateur band unless you actually purchased one and make an attempt?
All Yaesu radios can be programmed to operate outside of amateur bands by adding or removing internal jumpers. This is in the factory documentation.
It's very good info too if SHTF.
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How could you know the device can be programmed outside of amateur band unless you actually purchased one and make an attempt?
All Yaesu radios can be programmed to operate outside of amateur bands by adding or removing internal jumpers. This is in the factory documentation.
It's very good info too if SHTF.
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Is it not common practice for ham radio operators to acquire radio equipment originally INTENDED for operation OUTSIDE the amateur radio bands, and modify or program them for use on ham bands......
How many of the repeaters and radios in use today by ham radio operators are actually HACKED Motorola products INTENDED for use on public safety frequencies.........
Note that I am an ex Motorola engineer and I personally made many of these mods. One of the first contacts ever made on the then new 902 MHz ham band was between a pair of hacked 800 MHz Motorola STX radios operated between me on my roof, and another Motorola engineer at field day in a public park a couple of miles away. ISN'T THIS THE EXACT SAME THING.
I bought a Baofeng and a Radioddity radio, just in case they go away. Both are programmed for use on only amateur frequencies, but it is possible to enter non ham frequencies from the keypad IF you can figure out the non trivial menu structure. If this turns out to be a real serious threat, one would hope that these companies would offer a software load that we could flash into these radios to restrict their operation to amateur frequencies only. I would have no problem with thet since that is the only real lawful use of these radios, they have too much RF power for FRS or GMRS.
Anyone buy a HackRF ONE? I got one of those too. Receives and TRANSMITS on ANY FREQUENCY from 1 MHz to 6 GHz, albeit with very low power. The signal is pretty dirty too, not really suitable for ham or any other narrow band communications. Are there not plenty of RF amplifiers on Ebay and Amazon?
Great Scott Gadgets - HackRF One
How many of the repeaters and radios in use today by ham radio operators are actually HACKED Motorola products INTENDED for use on public safety frequencies.........
Note that I am an ex Motorola engineer and I personally made many of these mods. One of the first contacts ever made on the then new 902 MHz ham band was between a pair of hacked 800 MHz Motorola STX radios operated between me on my roof, and another Motorola engineer at field day in a public park a couple of miles away. ISN'T THIS THE EXACT SAME THING.
I bought a Baofeng and a Radioddity radio, just in case they go away. Both are programmed for use on only amateur frequencies, but it is possible to enter non ham frequencies from the keypad IF you can figure out the non trivial menu structure. If this turns out to be a real serious threat, one would hope that these companies would offer a software load that we could flash into these radios to restrict their operation to amateur frequencies only. I would have no problem with thet since that is the only real lawful use of these radios, they have too much RF power for FRS or GMRS.
Anyone buy a HackRF ONE? I got one of those too. Receives and TRANSMITS on ANY FREQUENCY from 1 MHz to 6 GHz, albeit with very low power. The signal is pretty dirty too, not really suitable for ham or any other narrow band communications. Are there not plenty of RF amplifiers on Ebay and Amazon?
Great Scott Gadgets - HackRF One
No air core yet. What brought it up was buddy and self were listening to some tracks and discovered the cables make huge difference. I have lots of superflex Tramflex RG8x but for the RcA cables stiff is ok. If the 30pf rg8x sounds as good the RG62 then will use that for live stage guitar cables.
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This decision, referenced in the "ban" order, deals with modification and the requirement of certification for radios, ostensibly marketed to hams, but that can "easily be altered" to TX outside of ham bands.
" ....... transmitters that have a built-in capacity to operate on CB frequencies and can easily be altered to activate that capacity, such as by moving or removing a jumper plug or cutting a single wire" fall within the definition of "CB transmitter" under Section 95.603(c) of the Rules and therefore require certification prior to marketing or importation. ...... "
https://transition.fcc.gov/eb/Orders/2006/DA-06-1334A1.html
So, it looks like if the radio came with a ham band only firmware, that could not be re flashed to operate TX outside of the ham bands, should be a simple solution to the lack of having an expensive certification. Once again, the FCC created CB disaster, bites amateur radio in the you know where.
It also seems that if the radio got certified, it is good to go on the ham bands until the certification is revoked.
The letter from the LMCC, which is referenced in a footnote from the "ban" order, is a public record and easily available online. It would be interesting to know what industry group instigated this, and my money would be on YaeComWood.
I honestly can't recall any time the FCC has ever given a rats rear end about what hams used, as long as everything stayed within the ham bands. As noted, making stuff work on ham frequencies, whether it started as certified land mobile stuff, or surplus junk that would otherwise go in the scrap pile, is a long standing tradition, indeed a virtue, of the amateur radio service. Experimentation is one of the justifications for having an amateur radio service. These have really gotten under someone's skin .....
Win W5JAG
What happens when a player in the Ham Radio market (Swan) decides to build a 200 watt CB set........you get the Siltronix 1011....."do not cut the yellow jumpers in the USA."
My money would be on the largest player in the LMR market world wide, Motorola, owning a 90% share of the domestic public safety market and a near 50% share world wide. They have always had an ear with the FCC, and use it to guard their turf. These $50 radios are viewed as a threat, especially those that ARE actually certified for part 90 use.
When the "YaeComWoods" of the world started making low cost radios certified for pubic safety and general LMR use, Mot got scared, and bought the parent company of Yaesu, Vertex Standard. They made it clear that they had no interest in amateur radio, and actually gave the Yaesu group back to the original Japanese family that founded the company. The Vertex Standard products were added to Motorola's portfolio and the two distribution units were merged.
"No interest in amateur radio" was serious enough to nearly kill the ham club in our plant. Then the building was sold and the new owners instituted a "no antennas" rule. Ham club gone.
I got some Puxing PX-777's about seven or eight years ago, in part because they were certified to part 90, a rarity then, and apparently now.
Here is the cert page:
OET List Exhibits Report
My radios will program below 150 MHz, into the two meter ham band, where they are in fact programmed, and are kept in our cars with a portable magnet mount antenna, as a cheap emergency just in case radio.
Win W5JAG
Here is the cert page:
OET List Exhibits Report
My radios will program below 150 MHz, into the two meter ham band, where they are in fact programmed, and are kept in our cars with a portable magnet mount antenna, as a cheap emergency just in case radio.
Win W5JAG
Ham coax for audio:
I measured some cable pairs found locally and in thrift stores. You can get them for as low as .50 cents.
Anyway the stereo 10' Monster cable measured 340pf and 380pf (two sides)
My MFJ 259B has 10pf internal capacitance so I subtracted 10pf from readings.
So 360 /10 =36pf per foot. But 10-15pf is from the two RCA connectors.
Then I measured Vampire Cable's stereo pair. Its 5' .
170pf -10 -15 is 31pf per foot. It beats Monster but if cables are stored in high humidty thae absorb water. We don't know the history on these samples.
I measured a 'pawn shop' 20' cable with 1/4" instrument plugs. I purchased it new and it has been stored in low hudimity.
Its a wooping (1250pf. -10 -15) /20 = 62 pf per foot.
Then to bring to a studio next week, I made a 6' RG62 B/U (belden 8255)
I measured with two Neutrik 1/4 connectors 114pf. / 6 = 19pf per foot.
Its less per foot if connectors are subtracted, pretty close to 14pf spec.
Don't think I'll do the rg8x as its spec is 30pf / ft so so no gain there.
Here are some pics of the RG62 cable. Its quite flexable with a stranded inner wire.
I measured some cable pairs found locally and in thrift stores. You can get them for as low as .50 cents.
Anyway the stereo 10' Monster cable measured 340pf and 380pf (two sides)
My MFJ 259B has 10pf internal capacitance so I subtracted 10pf from readings.
So 360 /10 =36pf per foot. But 10-15pf is from the two RCA connectors.
Then I measured Vampire Cable's stereo pair. Its 5' .
170pf -10 -15 is 31pf per foot. It beats Monster but if cables are stored in high humidty thae absorb water. We don't know the history on these samples.
I measured a 'pawn shop' 20' cable with 1/4" instrument plugs. I purchased it new and it has been stored in low hudimity.
Its a wooping (1250pf. -10 -15) /20 = 62 pf per foot.
Then to bring to a studio next week, I made a 6' RG62 B/U (belden 8255)
I measured with two Neutrik 1/4 connectors 114pf. / 6 = 19pf per foot.
Its less per foot if connectors are subtracted, pretty close to 14pf spec.
Don't think I'll do the rg8x as its spec is 30pf / ft so so no gain there.
Here are some pics of the RG62 cable. Its quite flexable with a stranded inner wire.
Attachments
The interconnects should not make any difference if the driving source has a low output impedance. CD players, phones, iPADs and other devices where the headphone jack is used fall into this category. A line stage or preamp should also if it was competently designed.......
The two places where cables really matter is the turntable, and as you illustrate, an electric guitar. Here the cable capacitance works with the inductance of the guitar pickup or phono cartridge to create a resonant pole. Any series resistance in the coil winding determines the "Q" of the resonant pole.
I stuck an LME49720 opamp phono stage INSIDE my turntable. Good frequency response, zero hum. Use Radio Shack garbage for interconnects....it doesn't care. I even thought about putting inside the head shell, but couldn't quite make it fit.