Know-How Exchange : Strategy

Charge Less (give it away for free?)
Have a contest with a sought-after prize for new subscribers
Have information that's not available anywhere else
Co-market with another tech company (that's offering free product, free services, etc.)
Focus on new niches (geographic, age, gender, demographic, etc.)

why your magazine lacks subscription? i think your tech magazine is generalizing the tech sector. it i think targets to all the segments of tech sector thus people don't understand the nature of your magazine.

is it true that your magazine targets tech sector generally? if yes then read on:

i think you better use specialization i.e. market segmentation strategy in order to increase your subscription.

tech sector can be divided into these following sectors:

Aerospace
Artificial Intelligence
Biotechnology
Software
Electrical Engineering
Photonics
Nanotechnology
Nuclear Physics
Robotics
Telecommunications

now you target any one of the sectors above and concentrate on that sector. this will give people an idea about your specialization. in tech sector you need specialization and not generalization. o.k.

Having an email preference center can influence if the subscriber will subscribe to e-newsletter. Samples of past issues to be included in the preference center (provided the past issues had interesting content to showcase) so subscriber can "see" why should they subscribe.

You can't "make" people do anything. In terms of offers, what you think is awesome and what someone else thinks is awesome are probably miles apart.

Which sector of the tech industry are you focusing on? What pain points do these people have? How will your offers pinpoint those points? What solutions will you offer?