Here they are, what you’ve all been waiting for…I need some help in bypassing or disabling the “loop” on this infernal machine…
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RFBsays
Excellent That unit uses the same RF deck (module) as it’s much earlier “endless loop” cassette counterpart.
HERE is a youtube video showing the necessary modification to feed the RF deck with external audio for live transmission.
Hope that helps!
RFB
amradiomansays
So apparently it’s a do-able thing… Thank you so much for all the help! I’m going to try this mod over the weekend…I will probably leave the un-used electronics inside and just put another jack or two on the back…also I will probably add an SO-239 to it as well and eliminate the antenna screw that’s back there…not much used for that wimpy little thing!
Dave KA0VQX
RFBsays
Experiment No problem. While researching for information on your unit, I read several archived forums, surprisingly mostly yahoo group discussions about this unit and the cassette counterparts and the modifying to accept live external audio.
Some of those who have done the modifications have also added audio circuits to improve the audio response a bit, though those modifications were not specific in their descriptions, it shouldn’t be too much trouble to do some experimenting on improving the audio response once you get the external audio driving the RF deck.
Keep in mind though that your unit, and those others with the endless loop cassette tape drives, suffers an “FM’ing” issue when certain modulation peaks are reached. This would cause the audio on an AM receiver to sound distorted when tuned center on channel. It would also cause a ton of splatter up and down the band during the modulation peaks. Fortunately there are discussions about that too and some have described the modifications done specifically to address the FM’ing issue. The audio improvement modifications focused around the op amp and how it’s set up for gain and frequency curve.
Some have simply used a higher value input capacitor to the op amp and get satisfactory results, while others went in and totally revamped the design parameters around the op amp, vastly improving it’s gain and frequency response curve. But those folks also noted that the FM’ing also increased with the improved, wider frequency response they now get out of the improved audio input circuit.
It’s unusual that FM’ing would take place in a hi-level modulation configuration unless there is inadequate isolation between the final/modulator stage and previous stages. It could be inadequate RF choking at the modulator, or too tight of coupling between the RF stages themselves.
These units, even the Talking House V5 were not designed or intended or meant for “broadcasting” in the sense that we describe broadcasting here. Selling houses versus playing records and being DJ are two totally different things. These transmitters were not designed for transmitting music and playing DJ. They were designed to send a simple voice message to nearby passing radios in cars to sell houses. It was end users who “morphed” these transmitters from their original intended operation to using them for entertainment broadcasting. Since there is no rule stating a person cannot do that, there is nothing wrong with using one to transmit entertainment radio. They were just not intended or designed around those parameters, thus modifications are necessary, even to the Talking House V5 to which that unit being modified by Radio Systems is called the “i-AM” transmitter.
However that modified THV5 unit called i-AM may very well have a serious problem regarding the modifications done by Radio Systems and FCC rule 15.2.1043. There is no evidence of any documentation at the OET or it’s database regarding approval of continuing to use an old certification to an original and that original certification be applied to the modified unit i-AM.
15.2.1043 specifically states no modifications may be done to the frequency generating circuits, PLL or other frequency control circuit, buffer and amplifier stages and no modifying of the modulator and finals.
The evidence to date shows the i-AM is modified at the modulator circuit and final biasing.
(a) Except as provided in paragraph (b)(3) of this section, changes to the basic frequency determining and stabilizing circuitry (including clock or data rates), frequency multiplication stages, basic modulator circuit or maximum power or field strength ratings shall not be performed without application for and authorization of a new grant of certification. Variations in electrical or mechanical construction, other than these indicated items, are permitted provided the variations either do not affect the characteristics required to be reported to the Commission or the variations are made in compliance with the other provisions of this section. Changes to the software installed in a transmitter that do not affect the radio frequency emissions do not require a filing with the Commission and may be made by parties other than the holder of the grant of certification.
Keep 15.2.1043 in mind while modifying that transmitter if you wish for it to continue to be legal under it’s certification. But if your just going to use it for experimenting, I wouldn’t loose any sleep over any modifying of the thing…unless you really beefed up the final or added a fat linear!
RFB
radio8zsays
How about using one of those cassette adapters (like this one) which are intended to allow tape players to connect to other audio sources? This would not require any modifications at all and should remove questions about losing certification.
Neil
RFBsays
Quick Way Yep that adapter would work just fine. However there is still the matter of the very narrow audio response, even more so going through the cassette head with an adapter.
OP’s unit is the later model with the “ISD” 90 second capacity chip so the adapter won’t do much good there.
RFB
amradiomansays
Yeah sort of… Yeah mine is sort of like those oldest ones with the cassette…but…mine has the 90 second digital loop built in as a module where the loop cassette player/recorder would have been…so, old, maybe older, but not oldest…
Excellent
That unit uses the same RF deck (module) as it’s much earlier “endless loop” cassette counterpart.
HERE is a youtube video showing the necessary modification to feed the RF deck with external audio for live transmission.
Hope that helps!
RFB
So apparently it’s a do-able thing…
Thank you so much for all the help! I’m going to try this mod over the weekend…I will probably leave the un-used electronics inside and just put another jack or two on the back…also I will probably add an SO-239 to it as well and eliminate the antenna screw that’s back there…not much used for that wimpy little thing!
Dave KA0VQX
Experiment
No problem. While researching for information on your unit, I read several archived forums, surprisingly mostly yahoo group discussions about this unit and the cassette counterparts and the modifying to accept live external audio.
Some of those who have done the modifications have also added audio circuits to improve the audio response a bit, though those modifications were not specific in their descriptions, it shouldn’t be too much trouble to do some experimenting on improving the audio response once you get the external audio driving the RF deck.
Keep in mind though that your unit, and those others with the endless loop cassette tape drives, suffers an “FM’ing” issue when certain modulation peaks are reached. This would cause the audio on an AM receiver to sound distorted when tuned center on channel. It would also cause a ton of splatter up and down the band during the modulation peaks. Fortunately there are discussions about that too and some have described the modifications done specifically to address the FM’ing issue. The audio improvement modifications focused around the op amp and how it’s set up for gain and frequency curve.
Some have simply used a higher value input capacitor to the op amp and get satisfactory results, while others went in and totally revamped the design parameters around the op amp, vastly improving it’s gain and frequency response curve. But those folks also noted that the FM’ing also increased with the improved, wider frequency response they now get out of the improved audio input circuit.
It’s unusual that FM’ing would take place in a hi-level modulation configuration unless there is inadequate isolation between the final/modulator stage and previous stages. It could be inadequate RF choking at the modulator, or too tight of coupling between the RF stages themselves.
These units, even the Talking House V5 were not designed or intended or meant for “broadcasting” in the sense that we describe broadcasting here. Selling houses versus playing records and being DJ are two totally different things. These transmitters were not designed for transmitting music and playing DJ. They were designed to send a simple voice message to nearby passing radios in cars to sell houses. It was end users who “morphed” these transmitters from their original intended operation to using them for entertainment broadcasting. Since there is no rule stating a person cannot do that, there is nothing wrong with using one to transmit entertainment radio. They were just not intended or designed around those parameters, thus modifications are necessary, even to the Talking House V5 to which that unit being modified by Radio Systems is called the “i-AM” transmitter.
However that modified THV5 unit called i-AM may very well have a serious problem regarding the modifications done by Radio Systems and FCC rule 15.2.1043. There is no evidence of any documentation at the OET or it’s database regarding approval of continuing to use an old certification to an original and that original certification be applied to the modified unit i-AM.
15.2.1043 specifically states no modifications may be done to the frequency generating circuits, PLL or other frequency control circuit, buffer and amplifier stages and no modifying of the modulator and finals.
The evidence to date shows the i-AM is modified at the modulator circuit and final biasing.
FCC 15.2.1043
§ 2.1043 Changes in certificated equipment.
(a) Except as provided in paragraph (b)(3) of this section, changes to the basic frequency determining and stabilizing circuitry (including clock or data rates), frequency multiplication stages, basic modulator circuit or maximum power or field strength ratings shall not be performed without application for and authorization of a new grant of certification. Variations in electrical or mechanical construction, other than these indicated items, are permitted provided the variations either do not affect the characteristics required to be reported to the Commission or the variations are made in compliance with the other provisions of this section. Changes to the software installed in a transmitter that do not affect the radio frequency emissions do not require a filing with the Commission and may be made by parties other than the holder of the grant of certification.
Keep 15.2.1043 in mind while modifying that transmitter if you wish for it to continue to be legal under it’s certification. But if your just going to use it for experimenting, I wouldn’t loose any sleep over any modifying of the thing…unless you really beefed up the final or added a fat linear!
RFB
How about
using one of those cassette adapters (like this one) which are intended to allow tape players to connect to other audio sources? This would not require any modifications at all and should remove questions about losing certification.
Neil
Quick Way
Yep that adapter would work just fine. However there is still the matter of the very narrow audio response, even more so going through the cassette head with an adapter.
OP’s unit is the later model with the “ISD” 90 second capacity chip so the adapter won’t do much good there.
RFB
Yeah sort of…
Yeah mine is sort of like those oldest ones with the cassette…but…mine has the 90 second digital loop built in as a module where the loop cassette player/recorder would have been…so, old, maybe older, but not oldest…
Dave VQX