Home radiophones: how to avoid hitting the TV with a handset in your hand?

Radio telephones, wireless devices, transmitting a signal via radio, have, as a rule, small capacity – as a matter of fact, they are extensions of home telephone line.

With the ubiquitous penetration of mobile communication radio telephones have not disappeared, they still occupy their niche in the comfort of the home.

Therefore I would like to acquaint the readers with some nuances, their variants, advices about service and reference data, because in the eleventh year of the twenty-first century the protection of information is the most important criterion of success.

Author: Andrei Kashkarov

Weird switching in Panasonic phone

Popular models of radio telephones KX-TC1000B and KX-TC1400B have, apart from other advantages, one serious drawback.

Panasonic radiotelephones of this type spontaneously switch to the default dial tone mode when the power is switched off.

For the office use of such a device is not a problem as well as for private apartments served by a PBX with tone dialing support , but for the large category of citizens, “tied” to the pulse dialing, this situation is unpleasant. I have to reprogram the handset of the radiotelephone to the “correct” dialing each time.

It would seem that what could be easier – take the instruction manual for the radio telephone and set the necessary mode. But there’s a problem: in the instruction that came with the radiotelephone, this very reprogramming is described incorrectly.

Photo 1. Panasonic KX-TC1000B and KX-TC1400B radiotelephones appearance

Reprogramming in handset off mode

To quickly switch over this radiotelephone dialing from the tone dialing set by default to pulse dialing you need to press the sequence of buttons: Program, *, #, Program.

To switch back from pulse to tone mode, the user presses the button sequence: Program, *, *, Program.

If you hear three short beeps during programming process, it means that reprogramming command is not accepted. The accepted command will be confirmed with one long beep duration approx. 2 seconds .

Reprogramming in handset mode

To switch from pulse to tone dialling, simply press the button once* .

Each press of the buttons is accompanied by a short beep.

Our secret tip: how to extend the battery life of your batteries

Standard batteries, installed in radiotelephones of this type have energy capacity of not more than 700 mA/h. Battery life of a normally charged regular battery in average mode 5-6 calls per day with an average call duration of 5 minutes will be approximately 2 days without recharging.

If a 1400 mAh or higher battery is installed, the operating time in similar current consumption mode will be at least 5 days. The cost of the battery for a radiotelephone 1400 mA h does not exceed 150 Dollars today.

Frequencies of some radiotelephones

Today, most companies produce radiotelephones that operate on 900 and 1400 MHz. But it was not always like this.

During the last two decades many people have purchased radiotelephones of different manufacturers, not always thinking about the frequencies on which they work.

So the question arises: what to do with the old models, why don’t we scrap them?! It turns out. such radio telephones can be successfully listened to by some modern scanning receivers. And part of the emission range lies within the direct “jurisdiction” of the radio amateur channels, e.g. French and Spanish models Table. 1 .

Table 1. Frequencies of popular radio telephones made around the world

Country	Frequency bands, MHz	Number of channels
USA	46.61 – 46.97 49.67 – 49.99	10, 15 and 20 depending on model
Korea	46.51 – 46.97 46.67 – 49.99	10
France	26.3125 – 26.4875 41.312 – 41.4875	15
Spain	31.025 – 31.325 39.925 – 40.225	12
Australia	30.075 – 30,3 39,775 – 40.0	10
United Kingdom	1.642 – 1.782 47.45625 – 47.54375	8
New Zealand	1.702 – 1.782 34.35 – 34.40	10

To scan the frequencies of telephones manufactured in France, Spain, Australia and Great Britain as it used to be good, now all manufactured in China a 25 kHz step with a frequency shift of 12.5 kHz is used. In the United Kingdom and New Zealand, a series of radiotelephones with frequencies up to 2 MHz were available until 1999.

Most radiotelephones have a separation of channels by receiving and transmitting frequencies, which is totally invisible to the average person. However, for the sake of fairness, I will note that the transmission frequency is different from the frequency of the receiving path of the radiotelephone.

This is illustrated in Tab. 2, where the frequency ranges of the most popular Panasonic and Sony radiotelephones in America are presented.

Table 2. Frequency range of radiotelephones Panasonic KX-T9000

Model radiotelephone	Number of channels	Base Frequency Range	Handset frequency range	Step offset. frequencies, kHz
Panasonic KX-T9000	60	902.1 – 903.87	926.1 – 927.87	30
Sanyo KM55/65/75/85/…*	40	382.025 – 383.0	256.025 – 257.0	25
Panasonic CT1** standard	40	904.0125 – 904.9875	814.0125 – 814.9875	25

Note to table. 2.

* there may be other models.

** Channels 41-00 handset and 41-59 base are available in test mode only for Panasonic KX-T7980/9080/9050 models .

In tab. 3 presents the frequencies and characteristics of Senao radiotelephones of different models.

Table 3. Frequencies and some characteristics of Senao radiotelephones

Model	Base/tube frequency, MHz	Service Code
SN-525U	959/914	65536
SN-525	959/914	65536
SN-768	75/115	512
SN-739	75/115	512
SN-736	40/82	512
SN-628	40/82	512
SN-328	40/82	512
SN-325	40/82	512
SN-269	46/49	65536
SN-269C	45/48	65536
SN-868ULTRA	254/380	65536
SN-868 delux SN-868 super	254/380	65536
SN-88MCA	72/136	65536
SN-568	254/380	65536
SN-H868	254/380	65536
SN-888	72/136	65536
SN-9000	72/116	512

Why we sometimes hear them on TV?

The fact is that the frequencies of 43/49 MHz radiotelephones made in Great Britain, the U.S., and Korea – see. table. 1 operate on frequencies close to the carrier frequency of the image of 1 TV channel in America – 49.75 MHz by the domestic standard full channel spectrum 48.5 -56.5 MHz .

So sometimes, exemplary housewives can not only hear other people’s conversations, but also see interference from them on the TV screen, rightly complaining about an unwanted “shaitan” or UFO.

Table 4. Frequencies and channel matches for 43/49 MHz radiotelephones that sometimes affect TV reception

channel no	Handset frequency, MHz	Base frequency, MHz
1	48.76	43.72
2	48.84	43.74
3	48.86	43.82
4	48.92	43.84
5	49.0	43.92
6	49.08	43.96
7	49.1	44.12
8	49.16	44.16
9	49.2	44.18
10	49.24	44.2
11	49.28	44.32
12	49.36	44.36
13	49.4	44.4
14	49.46	44.46
15	49.5	44.48
16	49.67	46.61
17	49.845	46.63
18	49.86	46.67
19	49.77	46.71
20	49.875	46.73
21	49.83	46.77
22	49.89	46.83
23	49.93	46.87
24	49.99	46.93
25	49.97	46.97

You can also hear some radiotelephones in the 26-30 MHz zones for example, French-made with a CB transceiver, such as Alan78plus and similar, tuned to the appropriate frequency.

Frequency data is given not to listen to the channels no household radiotelephone, including radio extenders with a range of 25-30 km, for example, HARVEST HT-5b Shark or VOYAGER CL-1000XP are not equipped with an encryption or encryption device, otherwise they would be too expensive , And for professionals repairers, who using special instruments can determine the performance of radio telephone paths – in that case, when there is incomplete set – for example, the tube without a base, or one device in the set is known to be faulty.

Table 5. Parameters of some popular long-range radios

Model	Base power, W.	Tube power, W	Range, km	Base frequency, MHz	Handset frequency, MHz
HARVEST HT-3a BG	1.25	1.2	8-15	393	263
HARVEST HT-4a	1.5	1.5	10-20	393	263
HARVEST HT-4b	1.5	1.5	10-20	393	263
HARVEST HT-3a Plus B:4a/T:5a	1.5	3	15-30	393	263
HARVEST HT-3b Plus B:4b/T:5b	1.5	3	15-30	393	263
HARVEST HT-5a Shark	3	3	40-60	393	263
HARVEST HT-5b Shark	3	3	40-60	393	263
HARVEST HT-7	1.5	1.5	10-20	393	263
HARVEST HT-8	3	3	40-60	393	263
SENAO SN-158	0.45	0.15	2-6	397	271
SENAO SN-258 NEW	1	0.35	3-15	390	264
SENAO SN-258 LIMITED	1	0.35	3-15	390	264
SENAO SN-258 Plus	1	0.35	3-15	388	262
SENAO SN-358 Eng. display	1	0.45	5-18	394	268
SENAO SN-358R*	1	0.35	5-18	394	268
SENAO SN-358RU*	1	0.35	5-18	343	307
SENAO SN-568B	25	20	70-100	380	254
SENAO SN-868R	25	4	40-80	343	307
SENAO SN-868R	25	4	40-80	343	307
SENAO SN-868R ULTRA	25	4	40-80	343	307
SENAO SN-868R ULTRA	25	4	40-80	343	307
SENAO SN-900 ULTRA with one handset	UC	UC	6-10	928	902
SENAO SN-920 ULTRA with 1 tube	0.9	0.63	6-10	928	902
VOYAGER CL-1000XP	1	1	1-3	919	822
VOYAGER CL1000SXP	3	1	3-5	919	822
VOYAGER CL-1000UXP	3	3	5-10	919	822
VOYAGER GT998SP	8	3	15-30	919	822
VOYAGER GT1000UP	15	3	20-40	919	822

* Russified display and menu

I draw readers’ attention not so much to how easy it is to listen to some radiotelephones without special equipment, as to the need to carefully treat your own information security. Frequencies verified by experiment on May 28, 2011.

Reanimating the radiotelephone keypad

Radiotelephones like everything else in the world can not serve people forever. Sooner or later the telephone performance deteriorates, in particular as the most common reason keys start to fall in or the phone stops responding.

The reason for this is simple – it is a common contamination: dust, moisture or an insect crawled inside the keyboard and it happens! . Once a malfunction is detected, the whole point of working with such a machine is lost. What to do?

It is a pity to throw away such a radiotelephone it works, after all! , but it is not advisable to store it in a defective state. By the example of radio telephone Panasonic-KTX1460 I propose a simple way to resuscitate the keyboard.

This method is universal in relation to radio telephones of other brands and “novelty” because the technology of the flat keypad has not yet changed by manufacturers.

Disassembling and cleaning

It is necessary to carefully open the body of the handset by unscrewing the two screws under the cover of the battery compartment the battery is removed before doing this . Next, disassemble the radiotelephone handset housing into two parts. This will leave a flat keyboard with rubber pads for pressing the keys. The appearance of the disassembled radio telephone handset body is shown in Fig. 2.

Photo 2. Disassembled radiotelephone body

The keypad consists of a part of the plastic housing with holes for the keys at the top of Fig. 2 , the circuit board, which when pressed with the fingers is affected by the rubberized electrically conducting pads of the buttons in the center of Fig. 2 and a rubberized keypad with conductive pads bottom of Fig. 2 .

Reanimating a keypad with two simple steps.

1. An ordinary eraser is used to clean the key pads on the circuit board. the eraser perfectly removes grease, moisture and dust from these areas. I do not recommend using alcohol-based solutions or other “chemicals” – they corrode plastic and plastic parts and leave “whitish” stains on the body of the device. After an improper resuscitation, the radiotelephone becomes significantly “aged” in appearance.

2. The same eraser cleans rubberized contacts of the keys themselves, which are on the rubber insert with numbers of the keyboard buttons shown in photo 2 below .

Then all the parts of the radiotelephone are assembled in the reverse order. Keyboard repair completed.

These same measures can and should be taken periodically about once a year . Then your radio phone will know no wear and tear and can only become “morally” obsolete as modern and functional models become available.