A lot more complicated than a Pantry Xmitter

[Radio Fixer]

Wideband recording of historical AM radiofrequency bands (radiomuseum.org)

I had a play of the video and a speed read.  Doubt I will be bothering to add the facility to my all ready overcrowded radio Den.

My interest some here

Gary

[ppppenguin]

A video recorder has the bandwidth to record this but there are two main problems I can see.

1: On all tape based recorders the recording isn't continuous. It has a disturbance or dropoout once per field. On broadcast grade recorders the recording can be continuous but it will be very much geared to the video waveform with its sync pulses and blanking intervals.

2: The dynamic range of a video recorder may well be marginal.

If you digitise the signals with an SDR the problem becomes one of data capture. I would guess that any reasonable PC can do this.

[Mike Watterson]

With digitising you need a lot more bits resolution for more bandwidth than one station. The resolution needed increases as the bandwidth increases.
Also the ADCs all have less real dynamic range than the number of bits resolution suggests.

Jeffery is quite right about the VCR issues, except the dynamic range is nothing like good enough even if you solved the sync issues. Perhaps you could record frame sync on audio track on edge (or maybe in the FM subcarrier on a VHS with a nicam tuner) and line sync (if needed) on Colour Under channel on a modified VHS.

The cheap SDRs based on an upconverter to more than 42MHz and a USB TV stick are nearly useless because they have only 8 bit ADC in the mode where MPEG stream decoder is bypassed.

[ppppenguin]

I have a dim memory of 2" quadruplex video recorders being used as high bandwidth data recorders at one time. From the 1950s to the 1970s they were almost certainly the highest bandwidth recorder of any type. Albiet at a very high cost and huge size.

Don't remember who sed them but it surely must have been military or NASA. Nobody else could have afforded them.

[PerdioPal]

You can do the same with much more success these days with an SDR, doesn't half eat disk space though. Useful to capture late night USA MW stations, all of MW can be recorded for later listening.

[Murphyv310]

This can be done with a cheap RTL SDR dongle, it doesn't need to eat up HDD space if you limit the section you are interested in, also used 1 and 2tb HDDs are available for pennies on ebay and elsewhere, have a word with your friendly Sky engineer you might land up with too many!

[Radio Fixer]

So is he on to something? Will it have value to folks who have old radios? The general tone here is negative.
There have been multi-freq pantry transmitters made but although it allows the radio to be tuned to different 'pseudo' stations it wont be an authentic experience as he is trying to create.

thanks Gary

[Mike Watterson]

This can be done with a cheap RTL SDR dongle, it doesn't need to eat up HDD space if you limit the section you are interested in, also used 1 and 2tb HDDs are available for pennies on ebay and elsewhere, have a word with your friendly Sky engineer you might land up with too many!

Not really as the ADC in SDR mode is only 8 bits and thus in reality about 7 bits real resolution. If you are content with 5 bits resolution for a weak station then dynamic range is only 4:1

Also the minimum frequency is about 42 MHz on most of these, so you need an upconverter for LW/MW/SW. You can buy pre-packaged adaptors for the RTL USB sticks.

The 14 bit ADCs discussed are a minimal solution and really to be able to replay a weak station as well as live with a good dual conversion receiver (or even a simple valve superhet) you'd want more than 14 bits.

The RTL stick is simply a cheap intro to SDR, and it did allow laptop to receive DAB here before they turned it off. It also works for the local Airband and VHF-FM. But apart from needing an up-converter it's only any use on LW/MW/SW with good RF tuning (dual gang), variable attenuator, pre-amp and up converter with maybe a 45MHz or 50MHz local oscillator. Then narrow band use due to lack of ADC resolution.

[Mike Watterson]

So is he on to something?  Will it have value to folks who have old radios?  The general tone here is negative.
There have been multi-freq pantry transmitters made but although it allows the radio to be tuned to different 'pseudo' stations it wont be an authentic experience as he is trying to create.

thanks Gary

It's more for archival / demonstration / museum use if or when more or all MW & LW stations are gone. Recordings of past times. Hence 14bit to 18 bit serious ADCs or SDRs and storage not an issue. You don't actually need an SDR, simply a good enough ADC, band filtering and an aerial.

It doesn't make any sense for regular listening. One way to simulate live radio on AM is to monitor the radio LO. A controller has a table of frequencies to stations and then controls a satellite receiver and a modulator driving an inductive loop to couple to the Radio RF. Inter station noise and signal strength can be simulated.

A "multiswitch" can connect to 4 x LNBFs on a 1m dish and pick up over 2,000 radio stations from four satellites. The basic model can feed 12 or 16 satellite receivers. This kind of system can do up to 16 satellites (probably using 3 to 5 off 80cm to 1.2m dishes) and the quattro feeds to a multiswitch can be amplified/split (as each is only 1 band and H or V) to easily feed 256 multiswitches each with 16 outputs.

I've a multiswitch with 5x LNBFs, 1.1m dish c/w transverse curved arm and a 12 out multi-switch. Used to have 4 in and 16 out.

A sky box will work as long as the quattro LBNF pointing at 28.2 is on the first port. Most of my sat boxes are Turkish HD with HDMI, SCART & 3.5mm jack, USB stick/HDD recording and cost €45 each. They work with single LNB, 4 port or 8 port switches (either simple or multi) or USALS/GotoXY motor drive.
I have 1 x Manhatten replaced by tuner on TV, so in store. The Skyboxes given away. A Humax HDR in store because switching between Freesat & non-Freesat a pain and only records on Freesat, even manually. Multiple coax to four rooms.
Three Turkish boxes have €6 or €10 FM transmitters sold (CE mark) for phone or MP3 to car radio. So every VHF-FM radio has three extra channels, 88.1, 88.5 & 92.7.

I might rig up a controller, About 12 years ago I did a PIC with 433MHz TX and keyboard which signalled to one with 433MHz RX (scavanged from video senders & then I bought modules) and IR TX. An RX from VCR on laptop serial port was used to learn the original codes.

[Murphyv310]

Hi.
Without sounding negative I really don't see the point of this.
In theory yes a VCR might work but why on earth would you want to record a chunk of Medium Wave and keep replaying it? It's like being firmly stuck in the past.
You can only sensibly listen to one broadcast at a time and all the rest may have no content you are interested in. For me build a quality pantry transmitter that is extremely easy to do and feed it with content you enjoy. Each to their own, but a VCR no way, I was sick of the sight of them in the trade and glad to see the back of them.