Wednesday, April 19, 2017

The Realistic Portavision - Portable Television in the 1980s

About a week or two ago on this blog, I may have foreshadowed that I had acquired a new electronic item worth talking about.  Portable televisions have always been of interest to me.  Since TVs became mainstream in the 1950s, marketers have always tried to find ways to make TVs smaller and able to be used in more and more places across the globe.  My little acquisition represents the peak of its technology for its time, so let's look at it in greater detail.

The system in question is called the Realistic Portavision.  Its most notable feature is that it is a fully portable color CRT TV.  A sticker on the back of the unit stated it was manufactured in November of 1985.  During the 1980s, portable TVs were not particularly rare.  Many kitchens and campers featured one.  But these TVs were typically black and white TVs.  Black and white TVs were much cheaper to manufacture, required fewer components to make them work and consumed less energy. Black and white TVs in portable sizes were quite common by the mid-1970s and were manufactured throughout the 1980s.

While a 15" TV set could be carried by one person without too much difficulty, at that size they were still rather unwieldy.  Moreover, they only came with AC plugs, requiring wall power.  Powering a TV set therefore meant finding a power source.  Portable generators weren't very convenient then and CRT TVs are not power efficient in the least.  Eventually, battery-powered TVs were released for sale, but they typically required quite a few C-cell or D-cell batteries to function.

On the front of the Portavision, there is the power button, a volume slider, a headphone jack and four buttons. The buttons have an 1980s aesthetic to them, they push in and out.  The buttons are colored in silver but are plastic, as is the front part of the Portavision.  The label piece appears to be brushed aluminum.  On the top is the carrying handle and the telescopic antenna.  On the right side is the tuning knob and the speaker.  On the left side are five TV tuning knobs, the AC cable connector and a DC connector port.  The single speaker also comes out of this side, which tends to bias the audio to the right side of the screen.  On the back are screw terminals for an external antenna, a coaxial jack, and composite video and mono audio RCA inputs and outputs as well as a pair of switches.

Let's start with the front panel.  The three buttons in the middle change the band to which the TV looks for a signal.  The Low VHF band covers channels 2-6, the High VHF band covers channels 7-13 and the UHF Band covers channels 14-83.  Channels are set with the tuning knob on the right side.  Because this TV was manufactured in the 1980s, it is looking for analog broadcast signals.  Congress mandated that full power TV station analog broadcasting cease on June 12, 2009 but the FCC allowed Class A TV station analog broadcasts until September 1, 2015.  Thereafter, only low power analog TV is allowed in the United States.  Moreover, any analog broadcasting cannot use channels 37 & 51-83.  There are no low power TV stations broadcasting in analog anywhere near where I live.

The rear panel is much more interesting.  The Portavision accepts composite input, but the small TV size means that there is little difference between RF and composite input from game consoles.  The RF and composite inputs allow game consoles to be easily used with the Portavision.  Most black and white portable TVs I have found only have an antenna.  Getting a signal from an RF cable to an antenna is not immediately obvious.  Plus, who wants to play games in black and white anyway?  Finally, there are composite outputs, so you can use this TV to record footage.  Typically this was intended to allow you to tape TV programs to a VCR, but today you could use it to record video gameplay footage.  By viewing the TV screen, you won't suffer from any latency.  However, you can only use the composite outputs to record from the antenna inputs, whether internal or external.  You cannot record from the composite inputs using this method.

When I first found the Portavision, I assumed that it had a radio TV tuner.  All the black and white TVs I have seen at thrift stores had radio tuners.  This one does not, otherwise it would have two more buttons for AM and FM bands.  The AM band is far below the FM band (525KHz to 1705KHz vs. 87.5MHz to 108MHz).  The FM band is between the Low VHF (54MHz-72MHz, 76MHz-88MHz) and High VHF (174MHz-216MHz).

The bottom has a battery compartment.  The TV requires 10 D-Cell batteries.  10 D-Cell batteries in series will give the TV its 12-15V it needs to run.  This adds significantly to the weight of the TV.  Also, the cost of the batteries back then was greater than nominal.  In order to make it easier to keep the batteries in place, there were plastic tubes included to keep them together.  There is also a kickstand to give the screen an angle for better viewing.

The left side has brightness, contrast, color, tint and vertical hold controls.  It also has a degauss button.  I guess the screen gets easily magnetized, but I haven't noticed it.  The controls for color and tint could have had a bump so you can easily determine the midpoint, but they do not on this TV.  The TV I have gives less than an ideal range of brightness and contrast, perhaps due to the age of the tube and components.  I am not sure if you can have a deep black with a strong white on this screen.  The AFT button on the front panel is supposed to be for Automatic Fine Tuning, but all it seemed to do for me was to boost colors.  The color boost was too much, so I kept that function off.  The screen of this TV is not the sharpest thing I have ever seen, but it can handle 40-column text, which will do for my purposes :

The vertical hold control was something that intrigued me greatly.  I have three other tube TVs, but none of them have a vertical hold control dial.  I have opened two of those TVs and could not find a pot or dial inside which functioned like a vertical hold control.  The third TV is of similar vintage, so I doubt it has an accessible control as well.

With the vertical hold signal, gaming with PAL consoles and home computers becomes possible.  I do not have any PAL machines in my possession at the moment, but my Atari 2600 can output as many scanlines as a program tells it to display.  NTSC games typically output 262-263 scanlines per frame, canonical NTSC video uses 262.5 scanlines per frame.  However, some NTSC Atari games can output have scanlines in the 240s, 250s, 270s or the 280s.  PAL Atari 2600 games typically output 312-313 scanlines per frame, but they can vary as well.  Canonical PAL video outputs 312.5 scanlines per frame.  PAL Atari 2600 games are typically not more detailed than their NTSC counterparts, the extra PAL lines do not typically display visual information, giving the graphics something of a squashed look compared to the same graphics stored on an NTSC TV.

The NTSC and PAL Atari 2600 may use different TIA chips for graphics and sound, run at a slightly different clock and generate different colors, but they function similarly enough that PAL software can almost always run in an NTSC machine.  However, the number of scanlines PAL software produces is enough to induce screen rolling on an NTSC TV.  This is where the vertical hold control comes in.  By adjusting this knob, I can stop the rolling.  Atari 2600 scene demos almost always use PAL-friendly scanline counts to give them more time in between the active display.  I was able to run several of these demos on this TV with no rolling.  The colors were off, but the only way to fix that is with a PAL 2600.

The PAL-friendliness of this TV will be useful if I wish to acquire a PAL C64 or a ZX Spectrum.  In order to display color from these machines, I will need a converter box that will translate PAL color into NTSC color because the TV should not be able to decode a PAL color signal.  The PAL color signal is more complex than the NTSC color signal.

Additionally, it may be possible to get a signal from the RF modulator inside the ZX Spectrum, which tunes to U.K. UHF channel 35.  The frequency range covered is 582-590MHz.  In the U.S., this lies between UHF channel 32 (578-584MHz) and 33 (584MHz-590MHz).  A TV with a dial or push button knobs is not likely to be able to tune to the right frequency.  You might get a fuzzy signal full of static and white noise.  Because this TV has a tuning dial, a more fine tuning may get a signal.  However, I am skeptical because U.K. channels require 8MHz of bandwidth while U.S. channels only require 6MHz.  In any event, the decoded signal would be B&W anyway.

What I did not know when I bought this TV from an estate sale was its origin.  The brand "Realistic" meant nothing to me, nor did the name "Portavision."  Hundreds of companies sold TVs over the years.  A Google search indicated that this TV was sold by Radio Shack.  RS sold many consumer electronics under its Realistic brand.  The Portavision was advertised in its Radio Shack catalogs alongside Tandy computers.  It was released in 1985 for $319.95, a pretty decent price for a portable color TV.  The 1985 Radio Shack General Catalog has a listing for it on page 104 and they specifically indicate that it can be used for as a computer video monitor or to function with a VCR.

Let me conclude with the following photograph :

Who needs an SX-64 when you have this!

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