Nokia N70 Mobile Car Mount

The Nokia N70 Mobile (Cellular) Phone is supposed (Nokia recommendation) to use the passive universal holder Nokia CR-39 when used in a vehicle. The Nokia CR-39 holder is simply a clamp, with no electric connections. When using this holder, it is necessary to connect the plug from the hands-free unit each time when entering the vehicle, and to disconnect the plug each time when leaving the vehicle. The Nokia CR-39 holder has no provisions for connecting an external antenna, and is therefore a primitive type of phone mount.


Nokia N70 phone mounted in the Nokia CR-27 holder


The passive Nokia CR-39 holder


Left photograph: The author's vehicle mounted Nokia N70 phone, residing in the Nokia CR-27 holder; at its bottom attached to the Nokia CA-55 cable from the Nokia CARK-91 hands-free kit, and attached to a charger cable from a separate 12 V DC charging adapter (the holder's bottom left). The holder's coaxial cable, for connecting the external antenna, protrudes from the rear of the Nokia CR-27 holder (not visible in this photograph; see the coaxial cable in the inside view photograph further below).

Right photograph: The passive Nokia CR-39 holder has to be clamped on and off each time you use the holder. The hands-free plug has to be plugged and unplugged each time you use the holder -- unless you use Bluetooth communication to the hands-free unit, but then you will have to plug and unplug the charger cable each time you use the holder. The Nokia CR-39 passive holder has no provision for connecting an external antenna, as seen from my photograph. External antenna connection inductors in the Nokia Antenna Adapter Series do not fit the Nokia CR-39 holder.

The Nokia CR-27 holder

The Nokia CR-27 holder is designed for the Nokia 6880 and 6881 phones, but can be used for the Nokia N70 phone. The holder is slightly deeper and slightly wider (to the left side, when considering the position of the phone connector) when used for the N70 phone. This may be adjusted by gluing some thin cardboard inside the holder, but for me it has not been found necessary.

The phone is simply pushed down in the CR-27 holder in an angle, and leaving it in its vertical position. The phone is released by pushing the phone down again, pulling it up in the same angle as when mounting it. The phone electrically connects to the Nokia "Pop-Port" connector at the lower end of the CR-27 holder.

The rear of the holder contains an inductive resonator for an indirect external antenna connection, which is possible to connect to the FME-type connector terminating the thin coaxial cable attached to the Nokia CR-27 holder.

The Nokia CA-55 Car Kit Converter Cable

The old hands-free units Nokia CARK-91 or CARK-109 can be used with this set-up using the Nokia CA-55 Car Kit Converter Cable between the hands-free unit and the CR-27 holder. The CR-27 holder may of course be used with other hands-free units, like the Nokia HF-3 and Nokia CK-7W (which both will charge the N70 phone; see the charging problem with the CA-55 cable below), and others.

Charging your N70 phone

Note that the CA-55 cable will not charge the Nokia N70 phone. This means that a separate vehicular battery charger has to be used, like the Nokia LCH-12. The CR-27 holder accepts a charger plug of the old Nokia "thick" type (not the new Nokia "thin" type used directly in the bottom part of the N70 phone).

There is not much room between the charger plug and the plug from the CA-55 cable. I found that I first had to connect the charger plug to the CR-27 holder, and then gently fit the plug from the CA-55 cable. With the design of the charger plug I had, it was impossible to do it in the opposite sequence. The correct position of the CA-55 cable is when its plug marking ("TOP" on the compatible version) is pointing towards you, the driver.

If this doesn't work, cut off 1 - 2 mm of the soft plastic on one side of the charger plug (to be facing the CA-55 cable plug) with a sharp pen knife (careful with your fingers). If the phone for some reason will not charge with this setup, take the phone out of its holder, turn the phone off, turn it on again, and put it in the holder. This procedure has helped me some times when the phone will not charge in the holder.

When putting the N70 phone in the wired CR-27 holder, the charger is noticed by the phone immediately. But it takes a few seconds before the N70 phone notices the hands-free unit (the phone is slow in this respect, like for a number of other functions). Next, the N70 phone activates the headset symbol on its display.

On my compatible charger, the LED (light emitting diode) is emitting a red light during charging pulses, and emitting a green light between charging pulses. When charging starts, the LED emits an almost constant red light; when the N70 phone is fully charged, the LED emits a contant green light. For some unknown reason, this information is not included in the charger package when purchased, and not found in technical specifications on the web.

Charging problems?

The CA-55 Car Kit Converter Cable will normally not charge your Nokia N70 phone. It appears that some (all?) CA-55 Car Kit Converter Cables have a short between pin 1 and pin 2 of their Pop-Port connector. (For information about the Nokia Pop-Port connector, see: These pins (No. 1 positive; No. 2 ground) support the charging of the phone. If the cable shorts these two pins, you will not be able to charge your phone, when using a separate charger like the Nokia LCH-12 or a compatible charger unit. The solution is to remove pin 1 of the CA-55 Cable Pop-Port Connector, see the circled connector in the photograph below. In my case it was possible to simply push the pin back into the connector with a small screwdriver, and filling the pin hole with a drop of enamel paint, to ensure that the pin would not make electric connection with the CR-27 holder.

The Nokia Pop-Port connector - the positive charging pin (No. 1) circled

Lack of mobile specific sensing profile

A number of other Nokia phones would activate a mobile profile when they sense that they are connected to a hands-free unit. Such a mobile profile would involve keeping the display light on, and the possibility to tailor the settings of the phone for vehicular use. This is obviously not possible with the Nokia N70 phone. Something to improve in further upgrades of the Nokia N70 firmware!

If the phone is set to some other profile than "General", the phone will automatically switch profile to "General" when used in the CR-27 holder. The "General" profile can then be set for vehicular use (e.g., with loud ringing), while you can create a new profile named "Common" for ordinary use elsewhere (e.g., with increasing ringing tone).

BTW, you can turn the light of the display on, and keep it on, manually, by buying the small program SmallTorch&NightClock by Very-Soft. When put in the CR-27 holder, and the SmallTorch&NightClock program running, the keyboard lock is turned off, like it should. But the keyboard lock is not turned on again when the phone is released from the holder. With the Nokia N70, running the SmallTorch&NightClock program, you unfortunately have to manually turn the keyboard lock on after using it in your car with the system described here. But by arranging your icons appropriately on your N70, this is quickly and easily done.

In Europe we use the designation "mobile phone" about the GSM phones, from the common use of such phones from vehicles. Obviously the Nokia N70 is no "mobile phone", but rather a "portable phone".

Would it be too much to ask Nokia to include a specific vehicular profile setting, with hands-free sensing, in future upgrades of the Nokia N70 firmware?

External antenna connection

Note that the Nokia N70 is a 4-band phone. It covers the two European (and International minus North America) GSM (= Global System for Mobile Communications) bands at 900 MHz and 1800 MHz, the North American 1900 MHz GSM band, and the newly utilized UMTS / WCDMA / "3G" (= 3rd Generation GSM) 2100 MHz band. I assume that the CR-27 holder is designed to transfer antenna signals on all four bands, because of the following excerpt from one of Nokia's press releases, found on the North American Nokia web page,1046,3072,00.html:

Introducing the first holder for UMTS phones
The Nokia Mobile Holder CR-27 is specially designed for use with Nokia's UMTS handsets including the Nokia 6680. Its elegant design complements the style of compatible mobile phones and there's an integrated dual-mode antenna coupler for connection to an external antenna, which gives users access to both GSM and UMTS networks.

An external antenna can be connected to the antenna cable protruding from the rear of the CR-27 holder. The antenna cable of the holder is connected to resonators in the rear of the CR-27, located opposite to (behind) the internal antennas of the N70. The resonators link to the antenna signals of the N70 by resonance induction. In the photograph below you see the red arrow pointing to the different membrane antenna resonators inside the CR-27 holder and their attachment to the coaxial antenna cable.

The red arrow points to the membrane antenna resonators inside the Nokia CR-27 holder

External antenna considerations

The challenge will then be to find a suitable wide-band antenna, which will permit transmitting on 900, 1800, and 2100 MHz (and 1900 MHz, if used in North America). My favorite mobile antenna maker PROCOM ( has made such antennas available. But the antennas available now is of quite low gain. To increase the antenna gain, it is possible to combine different colinear gain antennas with the help of suitable diplexers or triplexers to the coaxial cable leading to the CR-27 holder.

My vehicle antenna is the 60 cm long colinear PROCOM MU906-X, which primarily can be used between 800 and 1300 MHz, with 6 dB omnidirectional horizontal gain (4 times more effective radiated power, ERP) over a vertical dipole antenna at 900 MHz. The antenna works reasonably well on 1800 MHz too, and better than the built-in 2100 MHz antenna in the Nokia N70 phone. This antenna and the similar, but in-line designed, 65 cm long PROCOM MU908-X, are among the best GSM 900 MHz antennas available on the market in Europe. For long-haul GSM phone communication the lower frequency has a longer range. Therefore the antenna chosen should have its properties maximized at the lower GSM frequency.

If you want to use a fairly long (more than a few meters) coaxial cable, you must use a thick low-loss cable between your phone (CR-27 holder) and your antenna. The reason is that there are huge losses in the cables at such high frequencies. Some years ago one would use cables like RG-8 or RG-213. But during the last years we have got lower loss cables on the market, with even lower losses. You should check this with your local electronics supplier and buy the lowest loss cable possible (if you can afford it).

The antenna type is dependent on a number of things: What band(s) you want to operate, the radio path length, omnidirectional or directional characteristics. I suggest that you discuss your mobile telephone coverage problem with a local well-supplied supplier of electronics.

Parts source

All the components described here (except antennas and their accessories) are available at quite reasonable prices from Here they also sell a compatible "generic" CA-55 cable for much less than the original Nokia CA-55 cable, as they do for compatible "generic" 12 V DC charging cables / adapters. Note: The quality of the "generic" cable is not as good as the original Nokia cable. We have tried two "generic" cables. Both have had parts of their plugs broken after some time. It appears that Nokia is using a more flexible and hence more robust plastic in their cable plugs. I guess you get, as usual, the quality you pay for.

Battery considerations

Nokia has had bad experiences with non-Nokia batteries. Because of this Nokia recommends using only Nokia brand batteries. Nokia has recently marked their batteries with a hologram. But there are batteries on the market that promise more battery capacity for less money. How do they perform compared to the original Nokia batteries?


Batteries that can be used in the Nokia N70 phone


The MAHA MH-C777PLUS Universal Charger & Analyzer


The Nokia N70 phone is designed to use the Nokia BL-5C Li-ion rechargable battery (accumulator); see the lower left battery in the left photograph above. The nominal capacity of the Nokia BL-5C battery is 850 mAh (milli-Ampère-hours). It is also possible to use the Nokia BL-5B battery (lower right battery in the left photograph above) with a nominal capacity of 760 mAh. Note that the BL-5B battery has a smaller physical size than the Nokia BL-5C. The BL-5B may be used with the N70 phone by cutting a small piece of eraser, and placing it as a bottom extension to the BL-5B (see the bottom right in the left photograph above).

Two generic (non-Nokia) batteries were purchased, boasting 1300 mAh capacity for a fraction of the cost of the original Nokia BL-5C battery. One of the generic batteries had 1600 mAh capacity printed on its box, while printed 1300 mAh on the battery itself (see the upper two batteries and their boxes in the left photograph above). It was decided to test the capacities of all four batteries in the left picture above, using the Maha MH-C777PLUS Universal Charger & Analyzer (right photograph above). This charger is a "smart" microprocessor regulated charger, with the possibility to carefully discharge the battery completely before carefully charging the battery to its full capacity, displaying the battery's actual (real) capacity. The charger has a switch to facilitate charging Li-ion and nickel-metal-hydride / nickel-cadmium rechargable batteries.


The original Nokia BL-5C (nominal capacity 850 mAh) charged to 1332 mAh.

The original Nokia BL-5B (nominal capacity 760 mAh) charged to 1030 mAh.

The generic BL-5C (nominal capacity 1600 or 1300 mAh) charged to 754 mAh.

The generic BL-5C (nominal capacity 1300 mAh) charged to 717 mAh.


The original Nokia batteries tested have higher capacity than nominal, while the generic batteries tested have far less capacity than their boasted nominal values - and far less capacity than the original Nokia batteries. Nokia: Keep up the good work!

The Nokia Wireless Keyboard SU-8W

Stay tuned for some extra-manual information about this nice portable keyboard!

The Nokia Wireless Keyboard SU-8W

Oslo, 18 December 2005; revised 28 December 2006

Tom V. Segalstad