ICOM R75 radio review
Comparisons between ICOM R-75 and LOWE HF150
A very thorough refiew of ICOM R75 in two times arond 2001 and later (2005?)
Here you will see my impressions on my NEW R- 75 and how it was to oprerate this receiver. I have spent a lot of time ( more than 20 hours) to provide such information Together with it I will state soem comparisons with my previous HF150 of LOWE
updates are made with bue colour (see at the end of this file)
1. Impression on operation
Ergonomics and button operation: At first contrary to what I read in a web page , many buttons use more than one operation. For example by pressing SSB you can have either LSB or USB . Using other buttons such as filter , this information can be retained still after changing the operation mode . If you press AM and then SSB , it can show at first last active operation ( say LSB together with its bandwidth say wide LSB)
The tuning knob was very easy to use , somehow softer than the HF150 which recently has been stiffened too much that I can only use it with a screwdriver ààThere is also a adjustment knob for more stiffer usage
It also has the same facility with LOWE by having fast tuning together with its slow tuning. The tuning steps can be set from 0.1 to 50kHz steps but still there is a nice facility to tune it down to 1 hz ! Adjustments can be set either to MHz or to kHz but easily û by pressing the step knob for 2 secs the adjustment can come down to 1 Hz with full feq readout !
The most interesting button is the RF/SQL button. It can be set either as RF/ SQL( squelch) or only SQL . Its left part works for RF and in its right part works as Squelch. When adjusting to SQL the S meter indicator shows the squelch level for half a second or keeps clipping level
The second interesting button is the PBT with its twin passband . It works best in the narrow filters as I have not seen any differences while in normal or wide filters . In contrast to what I read , only the one knob ( the 2nd IF) is required to offset the frequency ( RIT) by 1.25 kHz only when the naroewest filter is selected ( 2.4)
Settings
: All modes and operations are easily set via the [SET/ ANT] button . When you push at once the set button rolls a menu with more than 20 settings starting from SQL/RF , to S indicator , LCD lighting ( with 1% steps tough on the screen 10% steps are only shown) and setting for the optional units as voice synth and also BFO settings for CW andRTTY It was somehow tricky however to adjust freqs for my MFJ reader 462 in order to properly tune in the range ( it required the lower setting of 1200 Hz forRTTY and abt 600 hz for CW. In some cases CW requires also external filter )
For filter setting there is another button, at same bank with mode buttons It is saved with the mode.In genaral by pressing any settings , it shows the last used operation
Modes: MOdes are set directly from the coresponding button right side from the LCD display There are some variants made by pressing the button for 2 secs (esp on CW an RTTY). Here are the modes i found with it
AM ........CW...........LSB...... RTTY.....FM
AMS.....CWN........USB......RTTYN....DSB*
CWN( Inverse) and RTTYN( Inverse) are made with the consistent pressing of the mode for more than 2 secs
DSB is made with a filter technique shown later . (see filtes)
Each mode (duringVFO) keeps the last selected filter and AGC
Noise blanker: I saw that Noise blanker can work relativel well under the SSB mode. However in many cases the MB can still work on AM but not always . Durign soem observations the AM NB mode can work when:
-AM is used on narrow band only
-you can use it in relatively low signal band ( as 9-9.2 MHz ) and only when a standard level of preampliication is given
AFC:
AFC operation is saved with the mode . Did not see any difference between normal and fast AFC on AM(/S) though in SSB worked properly . AFC-off does not show any signal in the S-unit and audio comes disturbed during normal AM
Bandwidth:
The receiver has normally 3 bandwidths 2.4 , 6 and 15 kHz and you can join them from the two IF stages and set them via a set menu . The 2+2 kHz filters are capable to off tune during NB AM operation soemtiems it ahppens also to 6kHz
During AM mode the 15 kHz surely can pass QRM from nearby stations but there is nearly no significant difference in audio fidelity when using headphones. This fidelity can be heard a little from the built in speaker
Filters :
There are many intereting points regarding to the filter selection. from the filter set mode. Each mode keeps diferent filter settings for the normal , wide and narrow band, however LSB and USB still keep the same filtering ( you cannot have dieferent seting for LSB Wide and USB wide) . same can happen to CW with CW inv, and RTTY with RTTY inv
Each filter mode ins mostly a combination of the 1st and 2nd IF filters or no combuination at all. The combinations are between 2.7, 6, 15 kHz or setting the 9 MHZ filter off ( then using only the 455kHz filter) . I could like to see however the receiver having a 4th combination when the optional filter is used.
Using the expanded filter mode you can expand the bandwidth of SSB towards a DSB operation for 6 and 15 kHz bandwidths thus having higher fidelity audio.
When you are on USB expanded operation by changing the mode to LSB is like to listen to the same signal .....
IN the case of listening to AM stations ,carrier is not totally deleted neither blanker efectively works
Expanded filter effects to all the modes.
CW /RTTY settings
: By pressing CW for more than 2 secs the CW operation is inverted , same happens toRTTY by choosing reverse mode ( and tuning again )
Sensitivity
: when using A/B testing with parallel listening theR-75 shown a slightly better sensitivity with preamp off. And LOWE was with ATT on ( and usage of two mini ear headphones)
Stability : The R-75 seems to be very stable also after hours of using. HF150 seems not so much as R-75
Display:( bad poits)
LCD display does not have any protective glass , so touching it the displayed information becomes nearly dull . Toching it also can produce some little noise eap in the lower bands ( LW- MW)
Preamplifier
: The preamp seems to work properly with good amplification in most cases also when using the loop with inductive coupling. See also on overloads
Memories:
There are only 99 memories plus 2 for scanning purposes. As i m not so keen on memorizing stations i thik these are OK for me. When you recall a memory and then tune, go to VFO and back to memory the previously tuned signal is lost.
All memories contain the following : freq, mode, AGC , amplifier, attenuator and antenna selection . Storing memories is very easy .R-75 offers also facility to skip unused memories. Mode retains the last used AGC
Signal indicator: It is a good facility and my best in my signal measurements .Stations can be still readable even the indicator canot show anything.However with signals higher than S9 the S meter seems not to correspond corectly in signal fluctuations and required from me to use the attenuator and the preamplifier in order to see the fading levels
Audio
:R-75 shown good audio from its internal speaker , sharper than LOWEÆs and comes only from the fidelity of the built in speaker . In the contrary using headphones the LOWE had better and higher fidelity sounds (good for HIFI reproduction while on AMS )
Audio is always clear and no background hiss is heard during no signal
Reception coments:
Am reception:
it is something I did not like so much. Most of the signals on AM mode can show some instability lower or greater depending on the fading level and speed On co-channel QRMed stations it can be a BIG problem , The Lowe does it much better without any instabilities.
AMS
: synchro mode shown no enhancement from normal AM ,. When the wide filter is used ( 15 kHz) and QRM is inside the determined bandwidth , signal is distorted . LOWE was much better by giving good signals without any distortion at any case even when there is some QRM inside the bandwidth The range the AMS with the 6 kHz filter can 'lock' (?) is +/- 3.3 kHZ then the BFO signal is heard !
SSB
: this is my most important point on this receiver. When reception on AM is not good , the SSB works excellent. The use of PBT ( and also with the usage of DSP noise canceller ) can provide very good results even in very low AM signals ( for less than SO11) so sometimes you can identify at least the language. I think that the SSB operation is better than the LOWEÆs also from the audio reproduction . As in result my MFJ audio filter is now useless in this point !Only the PBT of the narrow filter is mopstly required. In some cases the LSB mode took part from the carrier showing part of it though the USB showed the modulation of the signal (?) or must to tune off the passband
CW andRTTY
: It seems there is a audio filter fitted in the receiver though it is not very narrow ( esp for the CW operation)MY reader 462 in CW operation seem still to require the MFJ filter in order to read the poorer signals . As onRTTY after the trick by lowering the BFO the reader can recognize well the signals
FM mode: Unfortunately there are NO stations in our area using FM so i cannot give any opinions.
DSP operation
: despite whatÆs refered that DSP does not work on AM , I have seen good results as noise canceller and auto notch
The references ( and the book guide) shown that autonotch does not kill carriers. It is not true During my MW research on 11-2 the filter indeed,in auto notch mode can cancel-out any carriers at good levels if not completely It can also cancel out completely the BFO generated during offtune of an AM station when using SSB.
The DSP worked best with white noise but other noises ( such as from fluorescent lampsor other locally generated noises ) are ot completely cancelled, only from 10% to 40%
Levels up to 7 are working OK without masking except of cases of overmodulated audio signals or badly modulated signals ( such as poor modulation index or bad carriers found in greek pirates as example) with signal masked or truncated
Moreover , DSP in no operation produces clicks when you make freq adjustements from the freq nob
Overloads etc.
BDX reception:
Though I m living relatively close ( abt 15 km far) from the local MW stations all signals on MW band ( and even on the SW band ) did not exceed the S9 +40 db , neither the receiver shown any overload with preamp on . IN contrast to what is stated , I had good reception in the MW bands with the sloped 8 m antenna
As for example, 1044 , the local ERA station transmits with a 50 kW signal making a S9+30 dB . During nights the signals on the nearby freqs ( 1035+ 1053 at nearly S9 level ) are still heard without any signaificant problem except some little splatter when ERA plays music
SW reception
: There was no overload on any bands at any case. Many strong broadcast band stations do not exceed the S9+20 db limit . IN some cases the HF150 did overload or received some splatter from nearby strong signals butR-75 not.With the replacement of the 8 m antennas however to the 16 m antenna , there is some real overload especially in the SW band
Seflf generated carriers ( new) :
Using the technique of connecting a very short wire betwen the 500 ohm input and ground and full preamplification i hae found the follwing cariers
Stronger 456 kHz and 39982
Lower: 7995.....9997...11995...15990...19660...19990...21987...23003...27982...30000...31981...35977...39320...44236...
45971...47970...49150...51967...54065...55690...58980
There are still lower carrier but are too many to mention
Still under connection with the extenal antenna ther are soeme products generated found on 9370 and other s still not treid to see
VHF harmonics
R75
As usually he receiver generates some harmonics by its own,. I found that the armonic generates is exactly the 2nd harnmonic of local VFO plus the frequency used ie (VFO+ QRG) * 2 checked with the MVT7100 For erxample for 3500 becomes 145020 Also the change of the mode varies the harmonic according to the VFO used
As in result considering that with AM mode being x khz the frequencies found are as follws:
LSB........0.2
USB......6.4
FM.......3.3
CW......1.5
TTY.....1.2 kHz above the AM mode
Signal is ound to be S9 on the MVt7100 , attenuator on , with full antenna located on the left edgeof the receiver
HF150
Nearly the same happens with the Lowe HF150 according to the fiormula of (70MHz +QRG)* 2. In contrast to what is happened with R75 varrying smoothly with the frequency , the HF150 changes by the kHz freq so making a skip.
Signal S6 on the left edge of the receiver
Front panel harmonics
By sudden try the R75's front panel seems to generate soem mysterious harmonics esp on the 108-165 mHz band when the MVT was too close to it even with the R75 being off ( but not when plugged off the mains) . Do not know if this is an efect on the MVT's internal circuits or if it comes really fromthe R75 front panel but i have found that all this band was full of carriers with strongers bein on the follwing freqs ( signals were of S4 to >S10 being zero at a distance of 1-1.5 m )
115.5...117.96...120.42...122.88...132.7...137.62...140.08...142.54...150.98...153.6...154.82...157.28...162.2...
These carriers are also heard inthe R75's reecption on upper LW band
Overall
: Despite of the main problems ofR-75 with its synchro detector and its instability with co-QRMed stations om AM mode it is worth a buy . In general I like the receiver too much , much better than my previous LOWE HF150 especially for the very poor signals I live most. The nicer operation for me is the twin PBT that can enhance too much a DX reception and the slightly better sensitivity !Also the excellet S meter and frequency readout down to 1 Hz !
For any questions please send a mesage to me